Testing and Adjusting
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773D Off-Highway Truck 7ER00381-UP (MACHINE) POWERED BY 3412E Engine(SEBP ... Página Página 1 de 58 58 Cerrar SIS
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Producto: TRUCK Modelo: 773D TRUCK 7ER Configuración: 773D Off-Highway Truck 7ER00381-UP (MACHINE) POWERED BY 3412E Engine
Pruebas y Ajustes 773D TRUCK & 775D QUARRY TRUCK POWER TRAIN Número de medio -SENR1407-01
Fecha de publicación -19/09/1996
Fecha de actualización actualización -11/10/2001
Testing And Adjusting
Introduction NOTE: For additional details on the electrical system, see Electronic Programmable Transmission Control (EPTC II) Service Manual; SENR9122 NOTE: Automatic Electronic Traction Aid (AETA) and Automatic Retarder Control (ARC) may be referred to as Traction Control System (TCS) in other publications. Use the information in the book with the latest date. NOTE: For Specifications with illustrations, make reference to Specifications For 773D Truck and the 775D Truck Power Train, SENR1406. If the Specifications in SENR1406 are not the same as in the Systems Operation and the Testing and Adjusting, look at the printing date on the front cover of each book. Use the Specifications given in the book with the latest date.
Specifications Torque Converter Torque converter outlet pressure at stall speed ... 410 ± 70 kPa (60 ± 10 psi)
Inlet Relief Valve Torque converter inlet pressure ... 930 ± 35 kPa (135 ± 5 psi)
Secondary And Parking Brake Valve Parking brake release pressure at high idle setting ... 4690 ± 200 kPa (680 ± 30 psi)
Lockup Clutch And Synchronizing Valve Group Pressure Reduction Valve
Lockup clutch pilot pressure at high idle setting ... 1725 ± 70 kPa (250 ± 10 psi)
Modulation Reduction Valve
Lockup clutch maximum maximum pressure at low idle setting ... 1725 ± 70 kPa (250 ± 10 psi)
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Transmission
Transmission Hydraulic Control Group Pressure Control Valve Group
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773D Off-Highway Truck 7ER00381-UP (MACHINE) POWERED BY 3412E Engine(SEBP ... Página Página 2 de 58 58 Lockup clutch primary pressure at low idle setting ... 965 ± 35 kPa (140 ± 5 psi)
Transmission
Transmission Hydraulic Control Group Pressure Control Valve Group
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Selector And Pressure Control Valve Group Transmission Pump Pressure Relief Valve
Maximum pump pressure (at high idle) ... 3210 kPa (465 psi) Minimum pump pressure (at low idle) ... 2690 kPa (390 psi)
Priority Reduction Valve
Pilot pressure ... 1725 ± 70 kPa (250 ± 10 psi)
Transmission Lubrication Pressure Transmission lubrication pressure at high idle setting ... 140 to 205 kPa (20 to 30 psi) Transmission lubrication pressure at low idle setting ... 4 kPa (.5 psi) minimum
Brief Summary of Operation https://sisweb.cat.com/sisweb/sisweb/techdoc/techdoc_print_page.jsp?returnurl=/sisweb/sisweb/
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Power Train System Basic Diagram (Simplified)
1. The transmission speed sensor magnetically measures ground speed. 2. The Electronic Programmable Transmission Control (EPTC II) uses the signal from the transmission speed sensor to determine when to shift. The EPTC II activates the solenoids to make shifts. Monitoring System. 3. The input from the transmission speed sensor can be shared. The Cat Data Link connects the EPTC II with the Caterpillar Monitoring The speed distributor shares the information with Automatic Electronic Traction Aid (AETA) and Truck Payload Monitoring System (TPMS). 4. The body raise switch prevents REVERSE operation of the transmission during RAISE and LOWER operation of the body. The body up switch triggers the gear limit function, limiting the speed of the machine while the body is up. 5. The secondary/parking brake switch and service/retarder brake switch are inputs to EPTC II. When the secondary/parking or service/retarder brake switches are activated, activated, the anti-hunt timer timer is deactivated. The service/retarder service/retarder switch, when activated, will make make the shift speeds higher. 6. The shift lever switch selects desired speed and direction. 7. When an upshift or downshift solenoid is activated, it sends pressure oil to the rotary actuator, which turns the rotary selector spool. This sequence causes a different pair (two) of clutches to be engaged for the next speed. 8. Transmission hydraulic controls individually (separately) control the time to engage (fill time) and disengage (release time) each clutch and the maximum pressure in each clutch. 9. When the lockup solenoid is activated, pressure oil is sent to the modulation reduction valve of the lockup clutch valve. This sends oil to engage the lockup clutch of the torque converter for direct drive. 10. The transmission switch tells EPTC II what gear the transmission is in. The transmission switch is turned by the rotary selector spool. 11. The EPTC II sends a signal via the Cat Data Link to the Caterpillar Monitoring System and the gear is displayed on the instrument panel.
General Description
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Power Train System Basic Diagram (Simplified)
NOTE: For more details on the electrical system, please see Electronic Programmable Transmission Control (EPTC II) Service Manual; SENR9122.
The power train is made up of four basic systems. 1. Electronic Programmable Transmission Control (EPTC II). 2. Torque Converter. 3. Transfer Gears and Transmission. 4. Differential and Final Drives.
These four basic systems are connected to each other either electrically, hydraulically or mechanically. A basic diagram shows what components are common to each system. The operation of the power train begins at Electronic Programmable Transmission Control (EPTC II) (electrical system). EPTC II gets information of the selected speed of operation through the electrical system. The electrical system activates the hydraulic systems (transmission and torque converter) through solenoids (upshift and downshift solenoids). The solenoids (upshift and downshift) hydraulically activate the rotary actuator of the transmission. Movement of the rotary actuator mechanically selects the position of the rotary selector spool. The flow through the rotary selector spool hydraulically activates the correct valves in the pressure control group, to engage the correct transmission clutches. This mechanically connects the transmission input shaft to the output shaft and the differential. The transmission will not drive the output shaft unless there is power flow through the torque converter (either hydraulically or mechanically). The torque converter drives the transmission hydraulically, unless the lockup clutch is activated. When the lockup solenoid is activated, the lockup clutch is hydraulically engaged. The rotating (input) housing of the torque converter is now mechanically connected to the output shaft of the torque converter. The drive shaft mechanically connects the torque converter to the transfer gears. The transfer gears are mechanically connected to the transmission. After the transmission and torque converter are connected, power can now be supplied from the engine (through the transmission and torque converter) to the differential. The rear axles mechanically connect the differential to the final drives. When the transmission is in the correct speed position, the mechanical mechanical movement of the rotary rotary selector spool causes causes the transmission switch to electrically electrically signal the transmission transmission control that the shift is complete. With the rotation of the output shaft of the transmission, the transmission speed sensor electrically signals the transmission control that the machine has moved.
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Manual Shift Procedure During troubleshooting it is sometimes necessary to shift the transmission. This is done by turning the rotary selector spool when the engine is off.
NOTICE To prevent possible damage to the flexible coupling, never manually shift the transmission by rotating the flexible coupling for the transmission switch.
1. Remove the plug from the transmission case. 2. Install a 9S-1721 Extension [.25 (1/4) inch square drive] 101.6 mm (4.00 in) long in the end of the rotary selector spool. Install a 9U-6635 Reversible Ratchet on the extension. 3. Move the ratchet clockwise (toward the rear of the machine) until the rotary selector spool will not turn any more. This is NEUTRAL position. 4. From NEUTRAL position, turn the ratchet counterclockwise (toward the front of the machine) through all detent positions of the rotary selector spool. The positions from NEUTRAL are REVERSE, FIRST, SECOND, THIRD, FOURTH, FIFTH, SIXTH and SEVENTH speeds respectively. NOTE: There is approximately 30° of rotation between each detent of the rotary selector spool.
Ratchet And Extension Installed In The Rotary Selector Spool
Neutral Coasting This function restricts coasting into NEUTRAL from high speeds. This restriction extends transmission life. The transmission speed sensor measures the rotation of gear teeth (on a gear fastened to the output shaft of the transmission) near (past) the transmission speed sensor. Electronic Programmable Transmission Control (EPTC II) uses this input to determine the ground speed. If the measured speed is greater than 5 mph, the transmission will not shift into NEUTRAL. NOTE: It is possible for the operator to bypass the neutral coast restriction. However, if the ground speed is greater than 10 mph and the transmission is in NEUTRAL, the event will be recorded in the Caterpillar Monitoring System.
Adjustment For Hoist Control Linkage The hoist control linkage must be correctly adjusted when the machine is equipped with a transmission neutralizer.
The transmission on this machine will neutralize when the transmission shift lever is in REVERSE and the hoist control lever is in either RAISE or LOWER position. The neutralizer will not stop the machine from rolling. Use the brakes to stop. Make reference to WARNING on the first page of Hydraulic System Testing And Adjusting section.
Hoist Control Lever In The FLOAT Position (1) Hoist control lever. (2) Dimension [362 mm (14.25 in) from the top of cab floor plate without floor mat].
If the truck has a transmission neutralizer and the transmission does not go from REVERSE to NEUTRAL when hoist control lever (1) is moved to either the RAISE or LOWER position, a linkage adjustment may be necessary. An electric failure in the neutralizer switch or wires may also be the cause.
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773D Off-Highway Truck 7ER00381-UP (MACHINE) POWERED BY 3412E Engine(SEBP ... Página 7 de 58 Hoist control lever (1) is located to the left of the operator's seat. Dimension (2) must be 362 mm (14.25 in) from the top of the cab floor without the floor mat, to the bottom of the handle when the lever is in the FLOAT position. If the measurement for dimension (2) is not correct, the control linkage needs an adjustment.
Control Linkage Adjustment
Control Linkage Rods (3) Rod [from the shaft for the hoist control lever in the cab]. (4) R od [to the lever on the control valve in the hydraulic tank]. (5) Rod end.
1. Loosen the locknut on the end of rod (3) and remove the pin from rod end (5). 2. If the measurement for dimension (2) is too much, turn rod end (5) in the direction to make rod (3) longer. Make the length of rod (3) shorter if the measurement for dimension (2) is not enough. Measurements are done in a straight line between the centers of the rod end pin holes and the centers of the yoke pin holes.
The length for rod (3) is approximately 1589 mm (62.5 in). The length of rod (4) is 1083 mm (42.6 in).
Body Raise Switch Adjustment
Located In The Cab (6) Lockscrew. (7) Yoke. (8) Switch. (9) Low er roller. (10) Lever.
Before adjusting the location of the body raise switch, make sure the hoist control linkage dimensions are correct. 1. Remove the four bolts which hold the switch cover to the inside wall of the cab. Remove the cover from over the switch. 2. Move hoist control lever to the FLOAT position. 3. Lower roller (9) on yoke (7) must be near but not against the short lever (10) between the two rollers on the yoke. 4. If an adjustment to the position of yoke (7) i s necessary, move the hoist control lever to the FLOAT position. Loosen lockscrew (6) in yoke (7). 5. Yoke (7) is splined to the shaft of switch (8). Remove yoke (7). Rotate and reinstall yoke (7) so that lower roller (9) is close to but not against lever (10). Tighten lockscrew (6) and install covers. 6. If this does not work, make the length of rod (3) either longer or shorter until the lower roller on yoke (9) is very near the short lever when hoist control lever is in the FLOAT position. NOTE: When rod (3) is made longer, be sure hoist control lever can be easily moved to the LOWER position.
Troubleshooting The Power Train
Sudden movement of the machine can cause injury to persons on or near the machine. To prevent possible injury, do the procedure that follows before troubleshooting the power train.
1. Move the machine to a smooth horizontal location. Move away from working machines and personnel. Put the transmission shift lever in NEUTRAL position. Engage the parking and secondary brakes. Stop the engine. 2. Permit only two people in the cab (one operator and a service person). The machine operator must only operate the machine as told by the service person. The service person will look at all lights (LED's) or gauges. Keep all other personnel either away from the machine or in view of the operator. 3. Make sure the transmission rotary selector spool is in NEUTRAL position.
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773D Off-Highway Truck 7ER00381-UP (MACHINE) POWERED BY 3412E Engine(SEBP ... Página 8 de 58 For locations of components and electrical connectors, see the Electrical Schematic, SENR1418. For hydraulic components or pressure tap locations see the Torque Converter and Transmission Hydraulic Troubleshooting sections in this module. Visual Checks are the first steps when troubleshooting a problem. The visual checks will find the problems that can be more quickly corrected. If the visual checks do not show any problems, the Operational Checks are the next steps to follow. The operational checks will permit the identification of possible problems with the machine during operation.
Visual Checks Perform visual checks first when troubleshooting a problem. Make the checks with the engine stopped. Place the shift lever in NEUTRAL and the transmission rotary selector spool in Neutral. Engage the parking brake.
Check A Inspect the oil levels in the transmission and hydraulic oil tank. NOTE: Many problems in the power train are caused by low oil level or air in the oil. If the engine has not been s tarted and run for several minutes, this oil level check will make sure there is oil in the transmission and the engine can be started. If the machine has sat overnight or longer without the engine running, the oil level will be high. An accurate oil level check can be made after the oil is hot.
Check B Inspect all oil lines, hoses and connections for damage or leaks. Look for oil on the ground under the machine. NOTE: If oil can leak out of a fitting or connection, air can leak in. Air in the system can be as bad as not enough oil.
Check C Inspect the transmission control fuse, harnesses and electrical connectors (refer to the Electrical Schematic; SENR1418). With the key switch and disconnect switch OFF, check the 10 ampere fuse for the transmission. If the fuse is open (broken or missing filament) replace it. Inspect the electrical harnesses for damaged or broken wires. Disconnect each connector and look for bent, broken or pulled out (removed) pins and sockets. Also look for any foreign material inside the connectors. The connectors must be tightened with normal force. They must also disconnect with the same amount of force.
Check D Check the batteries. Turn the disconnect switch ON. Listen for the secondary steering motor to run for around 3 seconds. If the secondary steering motor fails to run, inspect the starting and charging system before Visual Check E.
Check E Inspect transmission oil filter, magnetic screen and suction, parking brake release oil filter and torque converter oil filter. NOTE: Parking brake release oil filter, transmission oil filter and torque converter oil filter each have an oil filter bypass valve. An oil filter bypass valve lets oil bypass (go around) the oil filter element(s) whenever the pressure difference between inlet oil and outlet oil at the oil filter gets too high. Any oil that does not go through the filter element(s) goes directly into the hydraulic circuit. Dirty oil causes restrictions in valve orifices, sticking valves, etc.
The pressure setting of the bypass valve in the parking brake release oil filter, the torque converter oil filter, and the transmission oil filter is approximately 250 kPa (36 psi). If any contamination is found in the filter elements or screens all components of the transmission (power train) hydraulic system must be cleaned. Do not use any damaged parts. Any damaged parts must be removed and new parts installed.
Check F Check Electronic Programmable Transmission Control (EPTC II). See SENR9122 for procedures.
Operational Checks The operational checks that follow are designed to educate (train) the service personnel in a correct troubleshooting procedure and method. The checks and procedures are set in a sequence to find most problem(s) and/or probable cause(s) quickly. These operational checks must be done in order, starting with Check 1. Do not go to the next check until either the problem in the previous check has been corrected, or instructed to do so. If the correct result for the check is found, as instructed in the procedure, go directly to the next check (or procedure for the trained service personnel). Take note of all WARNINGS and NOTICES in these checks. Never start the next check until you read and understand the warnings or notices. The checks that follow can be used to find many of the problems that will be found during the operation of the machine. These checks will also give an indication of the system in which the problems can be found.
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773D Off-Highway Truck 7ER00381-UP (MACHINE) POWERED BY 3412E Engine(SEBP ... Página 9 de 58 Machine Preparation For Checks 1. Engage the parking brake. Be sure the shift lever is in NEUTRAL and the transmission rotary selector spool is in NEUTRAL position. 2. Check all fluid levels on the machine (engine oil, engine coolant, hydraulic oil, differential, transmission, etc.). See 773D & 775D Operation And Maintenance Manual; SEBU6968 to determine the correct oils to use. Fill if necessary. NOTE: The oil levels can be above the FULL mark at this time. With the engine running, both transmission and torque converter oil must be at the normal temperature for operation. 3. The engine must be STOPPED. Do not start the engine until told differently. 4. The tachometer must be at zero rpm.
Some of the checks that follow must be done with the machine in operation. A trained machine operator will be needed. Whenever the engine is in operation, the machine operator must be in the cab with the parking and service brakes ENGAGED until told differently.
Lockup Clutch And Solenoid Valve Check Check 1.
This check determines if: The electrical signal gets to the lockup solenoid. The lockup solenoid electrically activates. Procedure: 1. Disconnect the cab harness plug from EPTC II and disconnect the harness connector for the LOCKUP solenoid. Put a jumper wire from Socket 1 to Socket 5 of the cab harness plug (for the transmission control). This will supply + 24 Volts through the machine harness to actuate the lockup solenoid. 2. Turn on the key start switch. Do not start the engine. 3. Touch the lockup solenoid chassis harness connector to the lockup solenoid. 4. Each time the connector touches the solenoid a "click" and/or "buzz" must be felt and/or heard. Problem 1:
The "click" and/or "buzz" is not felt or heard. Probable Cause: a. Bad lockup solenoid. b. Broken (open or grounded) wire or harness to the lockup solenoid. Check 2:
This check determines if: The lockup clutch pressure is correct. Procedure: 1. Disconnect the upshift solenoid and downshift solenoid harness connectors. 2. The transmission shift lever must be in NEUTRAL and the transmission rotary selector spool must be in the NEUTRAL position. 3. Using two 2-pin sure seal connectors and two 16-gauge wires (approximately 4.5 m (15 ft) long), make a jumper harness. Connect one of the ends of the jumper harness to the harness for the downshift solenoid. This will supply + 24 Volts because the downshift solenoid remains activated when the transmission is in NEUTRAL. 4. Connect a 4000 kPa (600 psi) pressure gauge to the pressure tap for the lockup clutch.
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Pressure Tap For Lockup Clutch
5. Start and run the engine at LOW IDLE. Connect the other end of the jumper harness to the harness for the lockup solenoid. The pressure on the gauge must read 1725 ± 70 Pa (250 ± 10 psi). Problem 1:
The pressure on the gauge is 0 kPa (0 psi) at all times. Probable Cause:
See Troubleshooting The Torque Converter Hydraulic System. Do Lockup Clutch Checks. Problem 2:
The pressure on the gauge is not 0 kPa (0 psi) when the lockup solenoid is not activated. Probable Cause:
See Troubleshooting The Torque Converter Hydraulic System. Perform Lockup Clutch Checks. Problem 3:
The pressure on the gauge is not correct when the solenoid is activated. Probable Cause:
See Troubleshooting The Torque Converter Hydraulic System. Perform Lockup Clutch Checks.
Transmission and Transmission Control Check Check 3.
This check determines if: * The transmission switch operates and is installed (timed) correctly. * The transmission clutches engage. * The Electronic Programmable Transmission Control (EPTC II) operates. Procedure: 1. Disconnect all electrical harness connectors from the upshift, downshift and lockup solenoids. Start and run the engine at LOW IDLE. 2. Engage the parking brakes and service brakes. The front brake ON-OFF valve on the instrument panel must be ON. 3. Do the shift sequence that follows for REVERSE and each FORWARD speed (FIRST, SECOND, THIRD, FOURTH, FIFTH, SIXTH and SEVENTH).
NOTICE
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Check the brake oil temperature gauge regularly. Do not let the brake (torque converter and hoist hydraulic) oil temperature get too hot during this shift sequence. This can cause damage to the brakes, torque converter and hoist hydraulic system. The brake and torque converter oil temperature indicator on the instrument panel, and the master action lamp will flash when the temperature is too hot to operate in this condition. When the brake (torque converter) oil temperature gets too hot, put the transmission in NEUTRAL and run the engine at approximately 1500 rpm until the temperature returns to the normal operating range.
Shift Sequence: a. Manually rotate the transmission rotary selector spool to the desired speed. After the manual shift is made, move away from the machine. b. Gradually increase engine rpm to approximately 1300 rpm or until the machine starts to pull through the brakes, whichever happens first. c. Look at the rear end of the drive shaft. When there is correct transmission clutch operation, only a small amount of rotation (less than one complete turn) will be seen, except in NEUTRAL. If the machine starts to pull through the brakes before 1300 rpm, there is no need to look at the drive shaft.
d. Decrease the engine rpm to LOW IDLE. Shift to the next speed position. Do Steps a, b, and c of the shift sequence again. This will help in the identification of a slipping (partially engaged) clutch. Continue this sequence for the remainder of the speeds until SEVENTH speed is made. Problem 1:
The machine starts to creep (move) forward before engine rpm gets to 1300 rpm. Probable Cause:
Brake System. See Air System And Brakes, SENR1412. Problem 2:
The drive shaft does NOT turn in NEUTRAL. Probable Cause:
See Troubleshooting The Torque Converter Hydraulic System. Perform Visual Checks. Problem 3:
When a shift is made to REVERSE or any FORWARD speed, the engine stops running. Probable Cause:
See Troubleshooting The Torque Converter Hydraulic System. Perform Visual Checks. Problem 4:
The drive shaft turns in one or more s peeds other than NEUTRAL, but the wheels do not turn. (Clutch or clutches not engaging in transmission.) Probable Cause:
See Troubleshooting The Transmission Hydraulic System. Perform Visual Checks. Problem 5:
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The transmission will not stay in the manually shifted (selected) speed position. Manual shifts are hard in any direction (upshift or downshift). Probable Cause:
Solenoid Leakage: * shifts to higher speed from the selected shift (bad upshift solenoid). * shifts to lower speed from the selected shift (bad downshift solenoid).
Torque Converter Hydraulic System Troubleshooting
Basic Diagram For Power Train System
The troubleshooting for the torque converter hydraulic system is divided into four sections: torque converter, lockup clutch, hoist and brake cooling. The reason for this division is to save time and make it easier to find the correct troubleshooting information. Make reference to the following warning and pressure tap locations for all checks and tests. If the problem area (torque converter, lockup clutch, hoist or brake cooling) is not known, perform the checks and tests in the order they are given. For all tests, the oil must be at normal temperature of operation.
Sudden movement of the machine or release of oil under pressure can cause injury to persons on or near the machine. To prevent possible injury, perform the procedure that follows before testing and adjusting the torque converter.
1. Move the machine to a smooth horizontal location. Move away from working machines and personnel. 2. Put the transmission shift lever in NEUTRAL position. Engage the parking brake. Stop the engine. 3. Permit only one operator on the machine. Keep all other personnel either away from the machine or in view of the operator.
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Pins Installed In Body Of Truck
4. Fully raise the body and install the two pins at the rear of the truck.
Hoist Control Linkage
5. Disconnect the hoist control linkage. Remove the cotter pin and the pin that connects the rod to the hoist control lever. 7. Make sure the transmission rotary selector spool is in NEUTRAL position. 8. Make sure all hydraulic pressure is released before any fitting, hose or component is loosened, tightened, removed or adjusted.
Test Equipment
NOTE: Electronic Control Analyzer Programmer (ECAP) or Electronic Technician (ET) may be used in place of the multitach.
If 1U-5481 Pressure Gauge Group and 1U-5482 Pressure Adapter Group are not available, the tools that follow are needed.
Transmission Speed and Torque Converter Information
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Schematic
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Torque Converter Hydraulic System Hoist Control Linkage (1) Lockup solenoid. (2) Selector piston for lockup clutch. (3) Load piston for lockup clutch. (4) Pressure reduction valve. (5) Lockup clutch and solenoid valve group. (6) Modulation reduction valve for lockup clutch. (7) Secondary and parking brake valve. (8) Relief valve for parking brake release system. (9) Passage to rear wheel brakes. (10) Inlet relief valve for torque converter. (11) Torque converter. (12) Oil cooler for torque converter and brakes. (13) Oil pump drive. (14) Parking brake release oil filter. (15) Torque converter oil filter. (16) Lockup clutch for the torque converter. (17) Screen. (18) Parking brake release section of oil pump. (19) Torque converter charging section of oil pump. (20) Torque converter scavenge section of oil pump. (21) Scavenge screen. (22) Left rear wheel brake. (23) Right rear wheel brake. (24) Hydraulic oil tank. (25) Torque converter and brake cooling return line. (26) Oil pump for hoist hydraulics and rear brake cooling. (27) Suction screen. (28) Oil cooler relief valve for rear brakes. (29) Control valve for hoist. (30) Return oil screen for hoist. (31) Suction screen. (A) Pressure tap for lockup clutch pilot oil. (B) Pressure taps for parking brake release oil. (D) Pressure tap for torque converter outlet. (E) Pressure tap for torque converter lockup clutch. (F) Pressure tap for torque converter inlet. (G) Pressure tap for left rear brake cooling (inlet). (H) Pressure tap for left rear brake cooling (outlet). (K) Pressure tap for right rear brake cooling (outlet). (L) Pressure tap for right rear brake cooling (inlet).
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(M) Pressure tap for brake cooling (cooler outlet). (N) Pressure tap for brake cooling (cooler inlet).
Location Of Components And Pressure Taps
Torque Converter Lines (Top View) (5) Lockup clutch and solenoid valve group. (10) Inlet relief valve for torque converter. (12) O il cooler for torque converter and brakes. (13) Oil pump drive. (14) Parking release oil filter. (15) Torque converter oil filter. (24) Hydraulic oil tank. (26) Oil pump for hoist hydraulics and rear brake cooling.
View A-A (11) Torque converter. (13) Oil pump drive. (18) Parking brake release section of the oil pump. (19) Torque converter charging section of the oil pump. (20) Torque converter scavenge section of the oil pump. (24) Hydraulic oil tank [not shown in true location]. (D) Pressure tap for torque converter outlet.
Back Of Torque Converter Housing (1) Lockup solenoid. (5) Lockup clutch and solenoid valve group. (10) Inlet relief valve for torque converter. (A) Pressure tap for pilot oil [RV]. (B) Pressure taps for parking brake release oil [PMP]. (D) Pressure tap for torque converter outlet. (E) Pressure tap for torque converter lockup clutch [LU]. (F) Pressure tap for torque converter inlet.
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Right Side Of Engine (M) Pressure taps for brake cooling (cooler outlet). (N) Pressure taps for brake cooling (cooler inlet).
Front Of Right Rear Wheel Brake (L) Pressure taps for brake cooling (inlet). (K) Pressure taps for brake cooling (outlet).
Front Of Left Rear Wheel Brake (G) Pressure taps for brake cooling (inlet). (H) Pressure taps for brake cooling (outlet).
Troubleshooting An Overheated Hydraulic System
Instrument Panel (1) Brake oil temperature gauge. (2) Brake and torque converter oil temperature alert indicator.
An overheating problem in the hydraulic system will probably be s een first through the Caterpillar Monitoring System. Brake oil temperature gauge (1) and brake and torque converter oil temperature alert indicator (2) get input from two sensors. There is a sensor located in the torque converter outlet valve and a sensor located in the brake oil cooling tube.
NOTICE Check the brake oil temperature gauge (1) regularly. Do not allow the brake oil, torque converter oil and hoist hydraulic oil temperature to get too hot during this test sequence. This can cause damage to the brakes, the torque converter, and the hoist hydraulic system. Brake and torque converter oil temperature alert indicator (2) is on the instrument panel, and the master action light is located to the right of the speedometer and RPM gauge. They will activate when the temperature is too hot to operate in this condition. If the alert indicators come on, reduce the load on the machine or slow retarding speed. Move the machine to a convenient place to park and keep the engine operating. Move the manual retarder lever all the way down to cool the oil.
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Brake Oil Temperature Gauge (A) Temperature reading of 110°C (230°F). (B) Temperature reading of 124°C (255°F).
Problem 1:
Brake oil temperature gauge (1) indicates that the oil temperature is too hot. The master action light and brake and torque converter oil temperature alert indicator (2) on the instrument panel is OFF. Probable Cause:
Electrical system. See 773D & 775D Truck Electrical System Schematic; SENR1418. Problem 2:
Brake oil temperature gauge (1) indicates that the oil temperature is NOT too hot. The master action light and brake and torque converter oil temperature alert indicator (2) is ON. NOTE: Brake and torque converter oil temperature alert indicator (2) activates at approximately 124°C (255°F). The indicator stays activated until the oil temperature decreases to approximately 110°C (230°F). Therefore, it is possible for the brake oil temperature gauge (1) to indicate that oil temperature is NOT too hot while the brake and torque converter oil temperature alert indicator (2) is activated. Probable Cause:
Electrical system. See 773D & 775D Truck Electrical System Schematic; SENR1418. Problem 3:
Brake oil temperature gauge (1) indicates that the oil temperature is too hot. Brake and torque converter oil temperature alert indicator (2) is activated. Probable Cause:
Improper operation of the machine. Reference: See the Operation & Maintenance Manual for 773D & 775D Truck; SEBU6968 for correct operating techniques of the brake and retarder system.
Operate the machine again. Make sure that engine rpm does not get below 1700 rpm. This will make sure enough oil flows through the torque converter and brake oil coolers to keep the oil at normal operating temperature. Problem 4:
The conditions in Problem 3 are still identical after the machine is operated correctly. Probable Cause:
A restriction in the brake oil cooling system. To determine if there is a restriction in the cooling system, remove the cover from the makeup oil tank of the brake hydraulic system.
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Example Of Oil Flow At Low Idle rpm
Start and operate the engine at LOW IDLE rpm in NEUTRAL. There must be a constant flow of oil from the inlet tube into the brake makeup oil tank.
Example Of Oil Flow At High I dle rpm
Increase engine rpm to HIGH IDLE. The oil flow must increase as shown.
Hoist And Rear Brake Cooling Oil Pump Located On Left Side Behind Hydraulic An d Transmission Tank (3) Hoist and rear brake cooling oil pump.
Location Of Parking Brake Release Oil Pump Section And Torque Converter Charging Oil Pump Section (4) Parking brake release oil pump section. (5) Torque converter charging oil pump section.
Location Of Rear Brake Oil Cooler Relief Valve (6) Rear brake oil cooler relief valve.
If oil flow is not as shown for LOW IDLE and HIGH IDLE, the cause could be: * Failure of the hoist and rear brake cooling oil pump (3), parking brake release oil pump section (4), torque converter charging oil pump section (5). Perform Visual Checks For The Hydraulic System in this module. * Rear brake oil cooler relief valve (6) pressure is set too low. Bench test rear brake oil cooler relief valve (6) located in the hydraulic tank, to determine if the pressure setting is correct. * Restriction in the hose assembly from the hydraulic tank to the brake makeup oil tank.
Visual Checks For The Hydraulic System Which Includes Torque Converter, Brake Cooling, And Hoist Hydraulic Systems Make reference to the WARNING on the first page of the Hydraulic System, Testing And Adjusting section.
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Perform the Visual Checks first before troubleshooting a problem. Make the checks with the engine OFF and the parking brakes engaged. Move the transmission shift lever into NEUTRAL. During these checks, use a magnet to separate ferrous particles from non-ferrous particles such as O-ring seals, aluminum, and bronze. The following visual checks are a part of the Troubleshooting section: Check 1. Oil level in the hydraulic tank. Check 2. Leakage. Check 3. Parking brake release oil filter. Check 4. Torque converter oil filter. Check 5. Torque converter scavenge screen. Check 6. Oil cooler screens. Check 7. Parts inside the hydraulic tank. Check 8. Inspect return oil screen. Check 1:
Check the oil level in the hydraulic tank. Look for air or water in the oil at the sight gauge. Many problems in the torque converter are caused by low oil level or air in the oil. Add oil to the hydraulic tank if it is needed. See the Operation and Maintenance Manual; SEBU6968 to determine the proper oil to use. Problem 1:
The oil level is too high. Probable Cause:
The rear seal of the engine crankshaft is allowing engine oil into the torque converter cover. Problem 2:
Right Side Of Engine (3) Oil cooler [for hoist and torque converter pump oil].
There is an indication of water in the oil. Probable Cause:
Failure of oil cooler (3) for the hoist pump oil to rear brakes. Problem 3:
There is an indication of air in the oil. Probable Cause:
Perform Visual Check 2. Problem 4:
The oil level is too low. Probable Cause: * Perform Visual Check 2. Add oil before any tests are done.
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Final Drive Plug
* Check the oil level in each final drive. Brake cooling oil can leak into the final drive. Check 2:
Inspect all oil lines, hoses and connections for damage or leaks. Look for oil on the ground under the machine. NOTE: If oil can leak out of a fitting or connection, air can leak in. Air in the system can be as bad as not enough oil. Check 3:
Inner Right Side Of Main Frame (1) Torque converter oil filter. (2) Parking brake release oil filter.
Remove parking brake release oil filter (2) and inspect the filter for foreign material. Problem 1:
Rubber particles are found. Probable Cause: * Seal failure. * Hose failure. Problem 2:
Shiny steel particles are found. Probable Cause:
Three Section Pump (4) Parking brake release pump section. (5) Torque converter charging pump section. (6) Torque converter scavenge pump section. (7) Torque converter housing. (8) Scavenge screen [inside housing].
Mechanical failure of parking brake release pump section (4). NOTE: Parking brake release oil filter (2) and torque converter oil filter (1) each have an oil filter bypass valve. An oil filter bypass valve lets oil bypass the oil filter element whenever the pressure difference between inlet oil and outlet oil at the oil filter gets too high. Any oil that does not flow through the filter element, flows directly into the hydraulic circuit. Dirty oil causes restrictions in valve orifices, sticking valves, etc.
The pressure setting of the bypass valve in torque converter oil filter (1) and parking brake release oil filter (2) is approximately 250 kPa (36 psi). Check 4:
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Inner Right Side Of Main Frame (1) Torque converter oil filter. (2) Parking brake release oil filter.
Remove the torque converter oil filter (1) and inspect the filter for foreign material. Problem 1:
Rubber particles are found. Probable Cause: * Seal failure. * Hose failure. Problem 2:
Shiny steel particles are found. Probable Cause:
Three Section Pump (4) Parking brake release pump section. (5) Torque converter charging pump section. (6) Torque converter scavenge pump section. (7) Torque converter housing. (8) Scavenge screen [inside housing].
Mechanical failure of the torque converter charging pump section (5). Check 5:
Make sure that the oil has been drained from the hydraulic tank and the torque converter for the next check. Measure the amount of oil removed from the torque converter.
Three Section Pump (4) Parking brake release pump section. (5) Torque converter charging pump section. (6) Torque converter scavenge pump section. (7) Torque converter housing. (8) Scavenge screen [inside housing].
Remove the torque converter scavenge screen (8) and inspect the screen for foreign material or a restriction. Problem 1:
More than 19 liters (5 U.S. gal) of oil is drained from the torque converter. Probable Cause:
Restriction in torque converter scavenge screen (8). Problem 2:
More than 19 liters (5 U.S. gal) of oil is drained from the torque converter and aluminum particles are found.
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Probable Cause:
Mechanical failure of the torque converter. Problem 3:
More than 19 liters (5 U.S. gal) of oil is drained from the torque converter. During Visual Check 7, shiny steel particles were found on the bottom of the hydraulic tank. Probable Cause:
Mechanical failure of torque converter scavenge pump section (6). Problem 4:
Iron or steel chips are found. Probable Cause: * Worn flywheel or starting motor gear on engine. Inspect the starting motor and flywheel gears. * Worn drive or driven gear on torque converter charging pump section (5).
Located Inside Left Frame Behind Hydraulic And Transmission Tank (9) Oil pump drive. (10) Hoist and rear brake cooling oil pump.
* Mechanical failure of oil pump drive (9). Drain and inspect the oil pump drive. Problem 5:
Rubber particles are found. Probable Cause: * Seal failure. * Hose failure. Problem 6:
Bronze particles are found. Probable Cause:
Worn lockup clutch in the torque converter. Check 6:
Right Side Of Engine (11) Screen.
Remove screen (11) and inspect the screen for foreign materials. Problem 1:
Rubber particles are found in screen (11). Probable Cause: * Seal failure.
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* Hose failure. Problem 2:
Aluminum particles are found in screen (11).
Located Inside Left Frame Behind Hydraulic And Transmission Tank (9) Oil pump drive. (10) Hoist and rear brake cooling oil pump.
NOTE: A small amount of aluminum particles from wear of hoist and rear brake cooling oil pump (10) is normal. Probable Cause:
Mechanical failure of hoist and rear brake cooling oil pump (10). Perform Visual Check 8. Problem 3:
Shiny steel and/or chrome particles are found in screen (11). Probable Cause:
Mechanical failure of a hydraulic cylinder or rod. Look at cylinder rods for scoring. Problem 4:
Large quantity of aluminum particles are found in screen (11). Probable Cause:
Mechanical failure of the torque converter. Check 7:
Hydraulic Tank (12) Suction screen [for torque converter charging and parking brake release oil (behind plate)]. (13) Suction screen [for hoist and rear brake cooling oil (behind plate)]. (14) Hoist return oil screen.
Drain the oil from the hydraulic tank. Remove outer cover of the tank. Inspect oil removed from and the bottom of the tank for foreign materials. Remove suction screen (12) and suction screen (13) and clean the screens. Remove the hoist return oil screen (14) and inspect the screen for foreign materials. Problem 1:
Rubber particles are found. Probable Cause: * Seal failure. * Hose failure. Problem 2:
Shiny steel particles are found. Probable Cause:
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Three Section Pump (4) Parking brake release pump section. (5) Torque converter charging pump section. (6) Torque converter scavenge pump section. (7) Torque converter housing. (8) Scavenge screen [inside housing].
Mechanical failure of torque converter scavenge pump section (6). NOTE: This would result in an excess amount of oil drained from the torque converter. See Visual Check 5. Problem 3:
Pieces of red nonferrous material are found. These pieces are part of the brake disc. Probable Cause:
Failure of the wheel brakes. Check 8:
Hydraulic Tank (12) Suction screen [for torque converter charging and parking brake release oil (behind plate)]. (13) Suction screen [for hoist and rear brake cooling oil (behind plate)]. (14) Hoist return oil screen.
Remove hoist return oil screen (14) and inspect the screen for foreign material. Problem 1:
Rubber particles are found. Probable Cause: * Seal failure. * Hose failure. Problem 2:
Shiny steel and/or chrome particles are found in hoist return oil screen (14). Probable Cause:
Mechanical failure of a hydraulic cylinder or rod. Look at cylinder rods for scoring. Problem 3:
Aluminum particles are found in hoist return oil screen (15).
Located Inside Left Frame Behind Hydraulic And Transmission Tank (9) Oil pump drive. (10) Hoist and rear brake cooling oil pump.
NOTE: A small amount of aluminum particles from wear of hoist and rear brake cooling oil pump (10) is normal.
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Probable Cause:
Mechanical failure of hoist and rear brake cooling oil pump (10). NOTE: If any of the above particles are found during any Visual Check, all components of the torque converter, brake cooling and hoist systems must be cleaned. Do not use any damaged parts. Any damaged parts must be removed and new parts installed.
Torque Converter Tests
Make reference to the Warning on the first page of Troubleshooting The Torque Converter Hydraulic System.
Test 1. Torque Converter Outlet Pressure This test will show if: a. The torque converter operates correctly. Procedure: 1. Install the 9U-7400 Multitach II Group on the engine. The 9U-7400 Multitach II Group can measure engine rpm by the use of either the photo pickup and reflective tape, or a magnetic pickup or tachometer generator. NOTE: Electronic Control Analyzer Programmer (ECAP) or Electronic Technician (ET) can be used in place of the multitach. 2. At pressure tap (D), connect a hose to the nipple. Connect a pressure gauge [2000 kPa (290 psi)] to the hose. 3. Start and run the engine at LOW IDLE rpm in NEUTRAL. 4. The drive wheels must not turn during a stall test. Make sure that air pressure is at the normal pressure for operation. Put the front brakes ON-OFF valve in the ON position. Engage the parking brakes and the service brakes. NOTE: If the brakes do not keep the machine from movement, put the machine against a solid object that will not move. 5. Make sure that the brake (torque converter) oil is at normal operating temperature. Check to make sure that HIGH IDLE and LOW IDLE rpm are correct according to Fuel Setting And Related Information Fiche. 6. Move the transmission shift lever to REVERSE position. 7. SLOWLY increase the engine rpm to full throttle. The machine will try to move. 8. The engine rpm must be 1825 ± 65 rpm with the torque converter in a stall condition. 9. The pressure on the gauge must be 410 ± 70 kPa (60 ± 10 psi).
NOTICE Do not keep the torque converter in a stall condition for very long periods of time. This will cause the torque converter, engine and brakes to get hot.
10. When this test is complete, put the transmission shift lever in NEUTRAL and stop the engine. Remove the test equipment. Problem 1:
High idle rpm is correct (Step 5), but stall s peed (rpm in Step 7) is too high. Torque converter outlet pressure is correct. Probable Cause:
Bad torque converter. Problem 2:
Torque converter outlet pressure is too low. The oil gets too hot during normal operation. Probable Cause:
Perform Test 2. Problem 3:
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Torque converter outlet pressure is too low. Probable Cause:
Perform Test 2. Problem 4:
Torque converter outlet pressure is too high. The oil temperature is not too hot. Probable Cause:
Check for a restriction in the oil lines or the oil cooler for the torque converter and brakes. Problem 5:
Torque converter outlet pressure is correct. The oil gets too hot during normal operation. Probable Cause:
See the section, Troubleshooting An Overheated Hydraulic System.
Test 2. Torque Converter Inlet Pressure
Inlet Relief Valve For The Torque Converter (3) Inlet relief valve. (4) Hose assembly [to hydraulic tank]. (F) Pressure tap [for torque converter inlet].
This test will show if: a. Inlet relief valve (3) for the torque converter is open. b. Inlet relief valve (3) is set correctly.
NOTICE Inlet pressure to the torque converter must not be over 930 ± 35 kPa (135 ± 5 psi) with cold oil. Higher pressures will damage the torque converter. Adjustment of inlet relief valve (3) must only be done during a bench test.
Procedure: 1. Make sure that brake (torque converter) oil is at operating temperature. 2. Disconnect hose assembly (4) from inlet relief valve (3). Block or plug the end of the hose assembly so that oil does not drain out of the hydraulic tank. 3. Install another hose to inlet relief valve (3). Put the other end of this hose in a container (bucket, pan, etc.). 4. At pressure tap (F), remove the plug and install a nipple. 5. With a coupler (and hose if necessary), connect a pressure gauge [2000 kPa (290 psi)] to the nipple. 6. Start and run the engine at LOW IDLE rpm in NEUTRAL. Immediately check the container to see if any oil is in it. 7. If there is any oil in the container, stop the engine. See Problem 1. NOTE: Connect hose assembly (4) to the inlet relief valve before Step 8 is performed. 8. If there is no oil in the container, gradually increase engine rpm to HIGH IDLE in NEUTRAL. The pressure on the gauge must not be greater than 930 ± 35 kPa (135 ± 5 psi) at any time. 9. When this test is complete, stop the engine. Remove the test equipment. Problem 1:
There is oil in the container (coming from the inlet relief valve).
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Probable Cause: a. Spool is stuck open in inlet relief valve (3). Disassemble the valve to correct the problem or install a new valve. b. Inlet relief valve (3) is set too low. Bench test the valve to see if it is adjusted correctly. The correct pressure setting is 930 kPa (135 psi). Add spacers (5), see Spacer Chart For Inlet Relief Valve. Problem 2:
Torque converter inlet pressure is too high. Probable Cause:
Inlet Relief Valve For Torque Converter (3) Inlet relief valve. (5) Spacers.
Bench test inlet relief valve (3) to see if it is adjusted correctly. Remove spacers (5), see Spacer Chart For Inlet Relief Valve.
Lockup Clutch Tests
Make reference to the warning on the first page of Troubleshooting The Torque Converter Hydraulic System.
Test 1. Parking Brake Release Pressure
Location Of Parking Brake Release Section Of Pump (1)
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Parking And Secondary Brake Control Valve (2) Parking brake relief valve.
This test will show if: a. Parking brake release section (1) of oil pump is good. b. Parking brake relief valve (2) is set correctly. Procedure:
Lockup Clutch And Solenoid Valve Group (B) Pressure Tap [for parking brake oil (PMP)].
1. Remove the plug at pressure tap (B). Install a nipple where the plug was removed. 2. With a coupler (and hose if necessary), connect a pressure gauge [10 000 kPa (1450 psi)] to the nipple. 3. With the parking brakes engaged, start and run the engine at HIGH IDLE rpm in NEUTRAL. The pressure on the gauge must be 4690 ± 200 kPa (680 ± 30 psi). 4. When the test is complete, stop the engine and remove the test equipment. Problem 1:
Oil pressure is low. Probable Cause: a. Failure of parking brake release section (1) of oil pump.
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Secondary And Parking Brake Control Valve (2) Relief valve [for parking brake release system]. (3) Nut. (4) Threaded rod. (5) C ap.
b. The setting of relief valve (2) for the parking brake release system is too low. Remove cap (5) and loosen nut (3). Turn threaded rod (4) clockwise to increase pressure. One turn increases the setting approximately 690 kPa (100 psi). Problem 2:
Oil pressure is too high. Probable Cause: a. The setting of relief valve (2) for the parking brake release system is too high. Remove cap (5) and loosen nut (3). Turn threaded rod (4) counterclockwise to decrease pressure. One turn decreases the setting approximately 690 kPa (100 psi).
Test 2. Lockup Clutch Pilot Pressure This test will show if: The pressure reduction valve is set correctly. Procedure:
Lockup Clutch and Solenoid Valve Group (A) Pressure tap for lockup clutch pilot oil (RV).
1. At pressure tap (A), remove the plug and install a nipple. NOTE: The nipple can be permanently installed at pressure tap (A). 2. With a coupler (and hose if necessary), connect a pressure gauge [4000 kPa (580 psi)] to the nipple. 3. With the parking brakes engaged, start and run the engine at LOW IDLE rpm in NEUTRAL. The pressure on the gauge must be 1725 ± 70 kPa (250 ± 10 psi). 4. Stop the engine. After the pressure is set correctly, remove the test equipment.
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Lockup Clutch And Solenoid Valve Group (6) Pressure reduction valve. (7) Shims.
Problem 1:
Oil pressure is too low. Probable Cause:
Add shims (7). See Shim Chart For Pressure Reduction Valve. Problem 2:
Oil pressure is too high. Probable Cause:
Remove shims (7). See Shim Chart For Pressure Reduction Valve.
Test 3. Lockup Clutch Leakage This test will show if: There are bad seals in the lockup clutch. Procedure:
Lockup Clutch and Solenoid Valve Group (E) Pressure tap [for torque converter lockup clutch (LU)].
1. Install a hose on pressure tap (E). 2. Start and run the engine at LOW IDLE rpm in NEUTRAL. 3. Measure the amount of oil that comes out of pressure tap (E) in one minute. Install fitting when this check is complete.
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Problem 1:
More than 3.8 liter/min (1 U.S. gpm) of oil comes out of pressure tap (E). Probable Cause:
Bad seals in the lockup clutch.
Test 4. Lockup Clutch Maximum Pressure This test will show if: a. Maximum lockup clutch pressure is correct. b. The operation of the modulation reduction valve is correct. Procedure:
Lockup Clutch and Solenoid Valve Group (8) Harness connector [for lockup solenoid]. (9) Lockup solenoid. (E) Pressure tap [for torque converter lockup clutch (L U)].
1. Disconnect electrical harness connector (8) from lockup solenoid (9). Disconnect the upshift solenoid and downshift solenoid also. 2. The transmission shift lever must be in NEUTRAL and the transmission rotary selector spool must be in the NEUTRAL position. 3. Using two 2-pin sure seal connectors and two 16-gauge wires (approximately 4.5 m (15 ft) long), make a jumper harness. Connect one of the ends of the jumper harness to the harness for the downshift solenoid. This will supply + 24 Volts because the downshift solenoid remains activated when the transmission is in NEUTRAL. 4. At pressure tap (E), use a coupler (and hose if necessary) and connect a pressure gauge [4000 kPa (580 psi)] to the nipple. 5. With the parking brakes engaged, start and run the engine at LOW IDLE rpm in NEUTRAL. Connect the other end of the jumper harness to electrical harness (8) for the lockup solenoid. The pressure on the gauge must be 1725 ± 70 kPa (250 ± 10 psi). 6. Remove the electrical harness connector from the lockup solenoid. The pressure on the gauge must go back to 0 kPa (0 psi). 7. Stop the engine. After the pressure is set correctly, remove the test equipment.
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Lockup Clutch And Solenoid Valve Group (10) Cover. (11) Selector piston. (12) Load piston plug. (13) Shims. (14) Outer spring. (15) Load piston orifice. (16) Inner spring. (17) Shuttle valve. (18) Spring. (19) Selector piston plug.
Problem 1:
Oil pressure in Step 4 is NOT 0 kPa (0 psi). Probable Cause: a. Selector piston (11) is stuck (will not go back to its original position). b. Weak or broken spring (18). c. Lockup solenoid (9) is bad (leaking). Problem 2:
Oil pressure in Step 5 is 0 kPa (0 psi). Probable Cause: a. Little or no pilot oil. Perform Test 2. b. Incorrect operation of chamber shuttle valve (17). c. Weak or broken spring (14) and/or spring (16). Problem 3:
Oil pressure in Step 5 does not increase above 965 kPa (140 psi). Probable Cause: a. Load piston plug (12) is not installed. b. Load piston orifice (15) is plugged. c. Selector piston (11) is stuck (will not move). Problem 4:
Oil pressure in Step 6 decreases slowly or low pressure remains (stays) in the lockup clutch. Probable Cause: a. Incorrect operation of shuttle valve (17). b. Selector piston (11) is stuck (will not move).
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Problem 5:
Oil pressure in Step 5 is too low. Probable Cause:
Perform Test 5. Problem 6:
Oil pressure in Step 5 is too high. Probable Cause:
Perform Test 5.
Test 5. Lockup Clutch Primary Pressure This test will show if: Lockup clutch pressure is adjusted correctly. Procedure: 1. Disconnect the upshift solenoid, downshift solenoid and lockup solenoid. 2. Using two 2-pin sure seal connectors and two 16-gauge wires (approximately 4.5 m (15 ft) long), make a jumper harness. Connect one of the ends of the jumper harness to the harness for the downshift solenoid. This will supply + 24 Volts because the downshift solenoid remains activated when the transmission is in NEUTRAL. 3. At pressure tap (E), use a coupler (and hose if necessary) and connect a pressure gauge [2000 kPa (290 psi)] to the nipple. 4. Remove cover (10) from lockup clutch and solenoid valve group. 5. Remove load piston plug (12) and install cover (10) again. 6. With the parking brakes engaged, start and run the engine at LOW IDLE rpm in NEUTRAL. Connect the other end of the jumper harness to electrical harness (8) for the lockup solenoid. The pressure on the gauge must be 965 ± 35 kPa (140 ± 5 psi). 7. Stop the engine. After the pressure is set correctly, remove the test equipment.
Problem 1:
Oil pressure is 0 kPa (0 psi). Probable Cause:
Selector piston plug (19) is not installed. Problem 2:
Primary pressure is too low. Probable Cause:
Add shims (13). See Shim Chart For Modulation Reduction Valve. Problem 3:
Primary pressure is too high. Probable Cause:
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Remove shims (13). See Shim Chart For Modulation Reduction Valve.
Transmission Hydraulic System Troubleshooting
Basic Diagram For Power Train Systems
Make reference to the following warning and pressure tap locations for all checks and tests of the transmission hydraulic system. If the problem area is not known, perform the checks and tests in the order they are given. For all tests, the oil must be at normal temperature of operation.
Sudden movement of the machine or release of oil under pressure can cause injury to persons on or near the machine. To prevent possible injury, perform the procedure that follows before testing and adjusting the transmission.
1. Move the machine to a smooth horizontal location. Move away from working machines and personnel. 2. Put the transmission shift lever in NEUTRAL position. Engage the parking brakes. Stop the engine. 3. Permit only one operator on the machine. Keep all other personnel either away from the machine or in view of the operator.
Pins Installed On Body Of Machine
4. Fully lift the body and install the two pins at the rear of the machine.
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Hoist Control Linkage
5. Disconnect the hoist control linkage. Remove the cotter pin and the pin that connects the rod to the hoist control lever. 6. Make sure the transmission rotary selector spool is in NEUTRAL position. 7. Make sure all hydraulic pressure is released before any fitting, hose or component is loosened, tightened, removed or adjusted.
Test Equipment
NOTE: Electronic Control Analyzer Programmer (ECAP) or Electronic Technician (ET) may be used in place of the multitach.
A minimum quantity of gauges and fittings needed: *
*
To save time on tests, use the quantity of gauges and fittings that follow:
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Transmission Speed And Clutch Engagement
Transmission Hydraulic Schematic
Typical Clutch Engagement For The Transmission Hydraulic System (1) Charging section of transmission oil pump. (2) Transmission oil cooler bypass valve. (3) Transmission oil filter. (4) Downshift solenoid. (5) Upshift solenoid. (6) Rotary actuator. (7) Selector piston for No. 3 clutch. (8) Load piston for No. 3 clutch. (9) Modulation reduction valve for No. 3 clutch. (10) Pressure control group. (11) Modulation reduction valve for No. 5 clutch.
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(12) Load piston for No. 5 clutch. (13) Selector piston for No. 5 clutch. (14) Transmission oil tank. (15) Transmission oil cooler. (16) Scavenge section of transmission oil pump. (17) Suction screen. (18) Magnetic screen. (19) Reservoir in transmission case. (20) Modulation reduction valve for No. 4 clutch. (21) Load piston for No. 4 clutch. (22) Selector piston for No. 4 clutch. (23) Priority reduction valve. (24) Neutralizer valve. (25) Rotary selector spool. (26) Selector group. (27) Selector piston for No. 1 clutch. (28) Load piston for No. 1 clutch. (29) Modulation reduction valve for No. 1 clutch. (30) Modulation reduction valve for No. 6 clutch. (31) Load piston for No. 6 clutch. (32) Selector piston for No. 6 clutch. (33) Selector piston for No. 2 clutch. (34) Load piston for No. 2 clutch. (35) Modulation reduction valve for No. 2 clutch. (36) Transmission lubrication relief valve. (37) Modulation reduction valve for No. 7 clutch. (38) Load piston for No. 7 clutch. (39) Selector piston for No. 7 clutch. (40) Relief valve. (41) Passage for transmission lubrication. (A) Pressure tap for No. 3 clutch. (B) Pressure tap for No. 1 clutch. (C) Pressure tap for No. 2 clutch. (D) Not used. (E) Pressure tap for No. 5 clutch. (F) Pressure tap for No. 4 clutch. (G) Pressure tap for No. 6 clutch. (H) Pressure tap for No. 7 clutch. (J) Pressure tap for upshift pressure. (K) Pressure tap for downshift pressure. (L) Pressure tap for pump. (M) Pressure tap for pilot oil.
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(N) Pressure tap for transmission lubrication. (AA) Main pump system pressure. (BB) Clutch oil. (CC) Pilot oil. (DD) Suction, return and case drain oil. (EE) Moving parts and activated valve envelopes. (FF) Lubrication oil.
Location Of Components And Pressure Taps
Transmission Lines And Filter (1) Charging section of transmission oil pump. (2) Transmission oil cooler bypass valve. (3) Transmission oil filter. (14) Transmission oil tank (section). (15) Transmission oil cooler. (16) Scavenge section of transmission oil pump. (18) Magnetic screen (inside transfer gear case). (N) Pressure tap for transmission lubrication.
Right Side Of Transmission (J) Pressure tap for upshift pressure (UP). (K) Pressure tap for downshift pressure (DN). (L) Pressure tap for pump (PRESS).
Left Side Of Transmission (N) Pressure tap for transmission lubrication.
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(A) Pressure tap for No. 2 clutch. (B) Pressure tap for No. 1 clutch. (C) Pressure tap for No. 7 clutch. (D) Not used. (E) Pressure tap for No. 5 clutch. (F) Pressure tap for No. 4 clutch. (G) Pressure tap for No. 6 clutch. (H) Pressure tap for No. 3 clutch. (M) Pressure tap for pilot oil.
(L) Pressure tap for pump. (M) Pressure tap for pilot oil.
Visual Checks
Make reference to the WARNING on the first page of Transmission Hydraulic System Troubleshooting.
Perform Visual Checks first when troubleshooting a problem. Make the checks with the engine stopped and the parking brakes engaged. Put the transmission shift lever and transmission rotary selector spool in NEUTRAL. During these checks, use a magnet to separate ferrous particles from non-ferrous particles (O-ring seals, aluminum, etc.). Check 1:
Check the oil level in the transmission oil tank. Look for air or water in the oil (through the s ight gauge). Many problems in the transmission are caused by low oil level or air in the oil. Add oil to the transmission oil tank if it is needed. See 773D & 775D Operation And Maintenance Manual; SEBU6968 to determine the correct oil to use.
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Inner Right Side Of Main Frame (1) Transmission oil filter.
NOTE: There is an oil filter bypass valve on the inlet side of the transmission oil filter. The oil filter bypass will open and let oil bypass (go around) the oil filter element whenever the pressure difference between inlet oil and outlet oil through the oil filter gets above 250 kPa (36 psi). Any oil that does not go through the filter element goes directly into the hydraulic circuit. Dirty oil will cause restrictions in valve orifices, sticking valves, etc. Problem 1:
The oil level is too high. Probable Cause:
Differential and bevel gear oil leaks into the transmission case because of: a. Failure of pinion seal in differential. b. Center plug of differential pinion is not installed or leaks. Problem 2:
There is an indication of water in the oil. Probable Cause:
Failure of the transmission oil cooler. Problem 3:
There is an indication of air in the oil. Probable Cause:
Perform Visual Check 2. Problem 4:
The oil level is too low. Probable Cause:
Perform Visual Check 2. Check 2:
Inspect all oil lines, hoses, and connections for damage or leaks. Look for oil on the ground under the machine. NOTE: If oil can leak out of a fitting or connection, air can leak in. Air in the system can be as bad as not enough oil. Check 3:
Inner Right Side Of Main Frame (1) Transmission oil filter.
Remove and inspect (cut apart if necessary) transmission oil filter (1) for foreign material. Problem 1:
Rubber particles are found.
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Probable Cause: a. Seal failure. b. Hose failure. Problem 2:
Shiny steel particles are found. Probable Cause:
Mechanical failure of the charging section of transmission oil pump. Check 4:
Bottom Of Transfer Gear Case (2) Magnetic screen (behind cover).
Remove and inspect magnetic screen (2) for foreign material. Problem 1:
Rubber particles are found. Probable Cause: a. Seal failure. b. Hose failure. Problem 2:
Bronze particles are found. Probable Cause:
Worn clutches in the transmission. Problem 3:
Iron or steel chips are found. Probable Cause:
Broken components in transfer gears or transmission. Problem 4:
Aluminum particles are found. Probable Cause:
Worn housings, load pistons or selector pistons in the pressure control group. Check 5:
Drain Plug For Transmission Case
Remove the plug from the bottom of the transmission case. This will drain all the oil out of the transmission and transfer gears. Measure the total
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amount of oil removed. Inspect the oil for foreign material. Problem 1:
More than 26 liters (7 U.S. gal) of oil is drained from the transmission and transfer gears. Probable Cause:
Bottom Of Transfer Gear Case (2) Magnetic screen (behind cover).
a. Restriction in magnetic screen (2). b. Failure of the scavenge section of the transmission oil pump. c. Too much leakage in a clutch or clutches of the transmission. Problem 2:
Rubber particles are found. Probable Cause:
Seal failure. Problem 3:
Bronze particles are found. Probable Cause:
Worn clutches in transmission. Problem 4:
Iron or steel chips are found. Probable Cause:
Broken components in transmission or transfer gears. Check 6:
Hydraulic Oil Tank (3) Suction screen.
Drain the oil from the transmission oil tank. Inspect the bottom of the oil tank for debris. Remove and clean suction screen (3). Problem 1:
Rubber particles are found. Probable Cause: a. Seal failure. b. Hose failure. Problem 2:
Shiny steel particles are found.
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Probable Cause:
Mechanical failure of scavenge section of the transmission oil pump. Problem 3:
Bronze particles are found. Probable Cause:
Worn clutches in the transmission. Problem 4:
Aluminum particles are found. Probable Cause:
Worn housings, load pistons or selector pistons in the pressure control group. NOTE: If any of the above particles are found during any Visual Check, all components of the transmission hydraulic system must be cleaned. Do not use any damaged parts. Any damaged parts must be removed and new parts installed.
Transmission Hydraulic System Tests
Make reference to the WARNING on the first page of the Transmission Hydraulic System Troubleshooting.
Test 1. Transmission Pump Pressure This test will show if: a. Charging section of the transmission oil pump is good. b. The relief valve is set correctly. Procedure:
Location Of Pressure Tap (L) For Pump (PRESS)
1. At pressure tap (L), use a coupler (and hose if necessary) and connect a pressure gauge [4000 kPa (580 psi)] to the nipple. 2. With the parking brakes engaged, start and run the engine at LOW IDLE rpm in NEUTRAL. The minimum pressure on the gauge should be 2690 kPa (390 psi). 3. Run the engine at HIGH IDLE rpm in NEUTRAL. The maximum pressure on the gauge should be 3210 kPa (465 psi).
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4. When this test is complete, stop the engine and remove the test equipment.
Selector Group (1) Relief valve. (2) Spacers.
Problem 1:
Oil pressure is too low. Probable Cause: a. Failure of charging section of transmission oil pump. b. The setting of relief valve (1) is too low. Add spacers (2), see "Spacer Chart for Relief Valve". Adjust for LOW IDLE setting. Problem 2:
Oil pressure is too high. Probable Cause:
The setting of relief valve (1) is too high. Remove spacers (2), see Spacer Chart for Relief Valve. Adjust for the LOW IDLE setting.
Test 2. Transmission Lubrication Pressure This test will show if: a. Oil pressure to the transmission lubrication circuit is good. b. The transmission lubrication relief valve is closed.
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Procedure:
Location Of Pressure Tap (N) For Transmission Lubrication
1. At pressure tap (N), use a coupler (and hose if necessary) and connect a pressure gauge [400 kPa (58 psi)] to the nipple. 2. With the parking brakes engaged, start and run the engine at LOW IDLE rpm in NEUTRAL. The pressure on the gauge must be a minimum of 4 kPa (.5 psi). 3. Run the engine at HIGH IDLE rpm in NEUTRAL. The pressure on the gauge must be 140 to 205 kPa (20 to 30 psi). 4. When this test is complete, stop the engine and remove the test equipment. Problem 1:
The transmission pump pressure is correct (Test 1). Transmission lubrication pressure is too low. Probable Cause:
Selector Valve (3) Transmission lubrication relief valve.
a. Transmission lubrication relief valve (3) is open. b. Too much leakage in the transmission lubrication circuit (bad seals, etc.). Problem 2:
The oil gets too hot during normal operation. Probable Cause:
Too much oil in transmission case. Perform Visual Check 5.
Test 3. Pilot Pressure
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This test will show if: The operation and setting of the priority reduction valve is correct. Procedure: NOTE: If Tests 4 and/or 5 are to be performed and FT1874 Transmission Test Cover is to be used, perform Steps 1 through 6 and go on to the next test. Pilot pressure can be checked while clutch pressures are checked. 1. Disconnect the wiring harness from the downshift solenoid and upshift solenoid. 2. Remove the solenoid guard and large cover from the transmission case. 3. Remove the plug from pressure tap (M). 4. Install a 3B-6552 Elbow [.125 (1/8 in) NPT] in pressure tap (M). Connect a 3B-7282 Nipple [.125 (1/8 in) NPT X 152 mm (6 in) long] with a 6V4142 Nipple to the elbow. 5. Put the large cover back on top of the transmission case. To prevent the release (spray) of oil and to keep dirt out, use a piece of plastic or paper along with the cover.
Alternate Step 5. Install the FT1874 Transmission Test Cover in place of large cover. Use four bolts evenly spaced to hold cover in place. 6. Connect a pressure gauge [4000 kPa (580 psi)] to the nipple. 7. Start and run the engine at LOW IDLE rpm in NEUTRAL. Keep the parking brakes engaged. 8. The pressure on the gauge must be 1725 ± 70 kPa (250 ± 10 psi). 9. When the test is complete, stop the engine.
Selector Group (4) Priority reduction valve. (5) Rotary selector spool. (6) Screen. (7) Spacers. (8) Neutralizer valve. (M) Pressure tap for pilot oil.
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Problem 1:
The pressure on the gauge is too low. Probable Cause:
The setting of priority reduction valve (4) is too low. Add spacers (7), see Spacer Chart for Priority Reduction Valve. Problem 2:
The pressure on the gauge is too high. Probable Cause:
The setting of priority reduction valve (4) is too high. Remove spacers (7). See Spacer Chart for Priority Reduction Valve. Problem 3:
The pressure on the gauge is correct, but the pressures at ALL clutches are 0 kPa (0 psi) (Test 4). Probable Cause: a. The operation of neutralizer valve (8) is not correct. Disassemble the selector group. Check for foreign material or worn or damaged parts. Make sure the orifice and/or ball check valve of the neutralizer valve are free o f any debris. b. Restriction in screen (6) in rotary selector spool (5). Problem 4:
The pressure on the gauge is correct, but the pressures at ALL clutches are too low (Test 4). Probable Cause:
Restriction in screen (6) in rotary selector spool (5).
Test 4. Pressure Control Group Clutch Pressures This test will show if: a. Transmission clutch pressures are correct. b. There is too much oil leakage in a clutch.
Sudden movement of the machine or release of oil under pressure can cause injury to persons on or near the machine. To prevent possible injury, perform the procedure that follows before Tests 4 and/or 5 are done.
1. Move the machine to a smooth horizontal location. Move away from working machines and personnel. 2. Apply the service brake. Put the transmission shift lever in NEUTRAL position. Engage the parking brakes. Stop the engine. 3. Permit only one operator on the machine. Keep all other personnel either away from the machine or in view of the operator.
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Pins Installed On Body Of The Machine
4. Raise the body and install the two pins at the rear of the machine.
Hoist Control Linkage
5. Disconnect the hoist control linkage. Remove the cotter pin and pin that connects the rod to the hoist control lever. 6. Make sure the transmission rotary selector spool is in NEUTRAL position. 7. Make sure all hydraulic pressure is released before any fitting, hose or component is loosened, tightened, removed or adjusted. 8. Remove both drive axles from the machine. 9. Make sure the test cover is installed on the transmission case before any tests are done. Procedure To Manually Shift The Transmission With The Engine Running (Drive Axles Removed)
This procedure will save time when the transmission is tested. Instead of the use of the transmission shift lever in the operator's station, shifts can be made down on the transmission. 1. Make sure the transmission shift lever is in NEUTRAL position. 2. Disconnect the wiring harness from the upshift solenoid, the downshift solenoid and the lockup solenoid.
Ratchet And Extension Installed In The Rotary Selector Spool
3. With the engine stopped, remove the plug (for the rotary selector spool) from the left side of the transmission case. 4. Use the .25 (1/4) inch square drive extension and ratchet to turn the transmission rotary selector spool. When the ratchet is turned clockwise as far as it will go, rotary selector spool (5) is in NEUTRAL position. The order of detent positions from NEUTRAL is REVERSE and FIRST through SEVENTH speeds respectively. Procedure: NOTE: If FT1874 Transmission Test Cover is used, a gauge can be installed at pressure tap (M) to check pilot pressure. If 6V-6064 Transmission Test Cover is used, make sure the plug is installed at pressure tap (M). 1. Remove the solenoid guard and large cover from the top of the transmission case. Install FT1874 Transmission Test Cover in place of the large cover. Use four bolts to hold the test cover in position.
Alternate Step 1. Remove small cover from large cover and install 6V-6064 Transmission Test Cover in place of the small cover. Use four nuts to hold the test cover in position.
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Pressure Test Gauge Installation (A) Pressure tap for No. 2 clutch. (B) Pressure tap for No. 1 clutch. (C) Pressure tap for No. 7 clutch. (D) Not used. (E) Pressure tap for No. 5 clutch. (F) Pressure tap for No. 4 clutch. (G) Pressure tap for No. 6 clutch. (H) Pressure tap for No. 3 clutch. (M) Pressure tap for pilot oil
2. At pressure tap (A), pressure tap (B), pressure tap (C), pressure tap (E), pressure tap (F), pressure tap (G), and pressure tap (H), connect pressure gauges [3400 kPa (580 psi)] to the nipples. 3. Start and run the engine at LOW IDLE rpm in NEUTRAL. 4. Make a record of the pressures on the gauges. Use the "Maximum Clutch Pressure Measurement" chart to record measurements. 5. Use the .25 (1/4) inch square drive ratchet and extension. Move transmission rotary selector spool (5) to REVERSE position. 6. Make a record of the pressures on the gauges. Use the "Maximum Clutch Pressure Measurement" chart to record measurements. 7. Manually shift the transmission into all forward speeds and make a record of the pressures on the gauges for each shift. Use the "Maximum Clutch Pressure Measurement" chart to record measurements. 8. With the transmission still in SEVENTH speed, increase the engine rpm to full throttle (HIGH IDLE). 9. Make a record of the pressures on the gauges. Use the "Maximum Clutch Pressure Measurement" chart to record measurements. 10. Decrease engine rpm to LOW IDLE and manually shift the transmission to SIXTH speed. Increase engine rpm again to full throttle (HIGH IDLE). Make a record of the pressures on the gauges. Use the "Maximum Clutch Pressure Measurement" chart to record measurements. 11. Do Step 10 again in all speeds including REVERSE and NEUTRAL. Make sure to decrease engine rpm before each downshift is made. 12. Stop the engine with the transmission rotary selector spool in NEUTRAL. 13. Make a comparison of the actual clutch pressures recorded on the "Maximum Clutch Pressure Measurement" chart, with the specifications given in the "Maximum Clutch Pressure Specifications" chart. 14. After the pressure is set correctly, remove the test equipment.
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Pressure Control Valve Group (9), (10), (11), (12), (13), (14) and (15) Modulation reduction valves. (16) Selector piston plugs (seven). (17) Load piston orifice (seven). (18) Decay orifice plug (six). (19) Load piston plug (seven). (20) Spring [inner (seven)]. (21) Spring [outer (seven)]. (22) Shims (seven places). (A), (B), (C), (D), (E), (F), (G) and (H) Pressure taps (also load piston body identification).
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Problem 1:
Pressures at ALL clutches are 0 kPa (0 psi). Probable Cause:
Pilot pressure. Do Test 3. Problem 2:
Pressures at ALL clutches are too low. Probable Cause:
Pilot pressure. Perform Test 3. Problem 3:
Pressure at ONE clutch is 0 kPa (0 psi). Probable Cause:
Selector piston plug (16) is not installed. Problem 4:
Pressure in a clutch does not increase above primary pressure. Probable Cause: a. Load piston plug (19) not installed. b. Load piston orifice (17) is plugged. c. Broken spring(s) in the modulation reduction valve. Problem 5:
An additional clutch gets pressure oil in some speeds (too many clutches are engaged).
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Probable Cause:
Perform Test 5. Problem 6:
Pressure in one clutch at HIGH IDLE rpm is not correct, but primary pressure in the same clutch is correct. Probable Cause:
Perform Test 5. Problem 7:
Primary pressure in one clutch is not correct, but pressure in the same clutch at HIGH IDLE rpm is correct. Probable Cause:
Perform Test 5. Problem 8:
Pressure in one clutch at HIGH IDLE rpm is correct, but pressure in the same clutch at LOW IDLE rpm is not correct (too low). Probable Cause:
Bad seals in a clutch of the transmission. Problem 9:
Pressure in one clutch does not decrease rapidly or low (approximately primary) pressure remains (stays) in one clutch. Probable Cause: a. Decay orifice is plugged. b. Drain orifice in rotary selector spool is plugged.
Test 5. Primary Clutch Pressures This test will show if: The clutch pressures are adjusted correctly.
Make reference to the WARNING given in Test 4.
Procedure: NOTE: Use the Procedure To Manually Shift The Transmission With The Engine Running (Drive Axles Removed) given in Test 4.
NOTICE Make sure the drive axles on the machine are removed for this test or the clutches of the transmission will be damaged.
1. If 6V-6064 Transmission Test Cover is used, remove small cover from the top of the transmission case. If FT1874 Transmission Test Cover is used, remove the large cover from the transmission case. 2. Remove seven load piston plugs (19) from their bodies. 3. Put the test cover back in position and install four bolts to hold it in place. 4. At pressure tap (A), pressure tap (B), pressure tap (C), pressure tap (E), pressure tap (F), pressure tap (G) and pressure tap (H), connect pressure gauges [1000 kPa (145 psi)] to the nipples. 5. Start and run the engine at LOW IDLE rpm in NEUTRAL. 6. Make a record of the pressures on the gauges. Use the Primary Clutch Pressure Measurement chart to record measurements. 7. Use the .25 (1/4) inch square drive ratchet and extension. Move the transmission rotary selector spool to REVERSE position. 8. Make a record of the pressures on the gauges. Use the Primary Clutch Pressure Measurement chart to record measurements.
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9. Manually shift the transmission into all forward speeds and make a record of the pressures on the gauges for each s hift. 10. Stop the engine with the transmission rotary selector spool in NEUTRAL. 11. Make a comparison of the actual primary clutch pressure, recorded on the Primary Clutch Pressure Measurement chart and the specification for each clutch given in the Primary Clutch Pressure Specifications chart. 12. After the pressures are set correctly, remove the pressure gauges and test cover. Install load piston plugs (19). 13. Install large cover, small cover and the solenoid guard. Connect the wiring harness to the solenoids.
Pressure Control Valve Group (9), (10), (11), (12), (13), (14) and (15) Modulation reduction valves. (16) Selector piston plugs (seven). (17) Load piston orifice (seven). (18) Decay orifice plug (six). (19) Load piston plug (seven). (20) Spring [inner (seven)]. (21) Spring [outer (seven)]. (22) Shims (seven places). (A), (B), (C), (D), (E), (F), (G) and (H) Pressure taps (also load piston body identification).
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773D Off-Highway Truck 7ER00381-UP (MACHINE) POWERED BY 3412E Engine(SE ...
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Problem 1:
Pressure at one clutch is 0 kPa (0 psi). Probable Cause:
Selector piston plug (16) is not installed. Problem 2:
Primary pressures at all clutches are 0 kPa (0 psi). Probable Cause:
Pilot pressure. Perform Test 3. Problem 3:
Primary pressures at all clutches are too low. Probable Cause:
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773D Off-Highway Truck 7ER00381-UP (MACHINE) POWERED BY 3412E Engine(SE ...
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Pilot pressure. Perform Test 3. Problem 4:
Primary pressure at one clutch is too low. Probable Cause:
Add shims (22) for the modulation reduction valve of the clutch that has low pressure. See "Shim Chart Pressure Control Group". Problem 5:
Primary pressure at one clutch is too high. Probable Cause:
Remove shims (22) for the modulation reduction valve that has high pressure. See "Shim Chart For Pressure Control Group". Problem 6:
An additional clutch gets pressure oil in some speeds (too many clutches are engaged). Probable Cause: a. A selector piston is stuck (will not go back to its original position). b. Weak or broken inner spring (20) for the modulation reduction valve. Problem 7:
Pressure in one clutch at HIGH IDLE rpm is not correct, but primary pressure in the same clutch is correct. Probable Cause: a. Wrong outer spring(s) (21) installed in the modulation reduction valve. b. Weak or broken outer s pring(s) (21) in the modulation reduction valve. c. Load piston orifice (17) is plugged. Problem 8:
Primary pressure in one clutch is not correct, but pressure in the same clutch at HIGH IDLE rpm is correct. Probable Cause: a. Wrong outer spring(s) (21) installed in the modulation relief valve.
Differential And Final Drives Troubleshooting
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773D Off-Highway Truck 7ER00381-UP (MACHINE) POWERED BY 3412E Engine(SE ...
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Basic Diagram For Power Train System
Visual Checks Use these Visual Checks as a guide to troubleshooting a problem. Make the checks with the engine OFF and the parking brakes ON. During these checks, use a magnet to separate ferrous particles from non-ferrous particles (O-ring seals, bronze, etc.). Check 1:
Remove the fill plug and check the oil level in each final drive. Make sure that the drain plug is down (in its lowest position) as shown, when the oil level is checked. Check for oil leakage on the rear tires and wheels. See 773D & 775D Operation And Maintenance Manual; SEBU6968 to determine the correct oil to use if filling is necessary.
Drain Plug And Fill Plug For A Final Drive
Problem 1:
The oil level in a final drive is too high. The oil level in the hydraulic oil tank is too low. Probable Cause:
Brake cooling oil leaks into final drive. Failure of small Duo-Cone seal at the rear wheel brake. Drain final drive and add new oil after a new seal is installed. Problem 2:
The oil level in a final drive is too low. Probable Cause:
Failure of O-ring seal on final drive housing. Check 2:
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