Transmission Control Valve

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Welcome: r15daxz Product: MOTOR GRADER Model: 12H NA MOTOR GRADER 4XM Configuration: 12H Motor Grader 4XM00001-UP (MACHINE) POWERED BY 3306B Engine

Systems Operation 120H, 12H, 135H, 140H, 143H, 160H and 163H Motor Graders Power Train Media Number -SENR8503-03

Publication Date -01/12/2005

Date Updated -15/12/2005

i03497742

Transmission Control Valve SMCS - 3073

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Illustration 1

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(1) Transmission control valve (2) Transmission wiring harness

Transmission control valve (1) provides the proper flows and the proper pressures in order to engage the desired transmission clutches. The transmission control valve is located on the left side of the transmission case. The transmission control valve is constructed of two cast aluminum valve bodies, three cast aluminum manifolds, three steel plates, several aluminum spools, and miscellaneous steel parts.

Illustration 2

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(3) Manual modulation valve (4) Main relief valve (5) Priority reducing valve (6) Modulating reducing valves (7) Solenoid valves

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The transmission control valve consists of the following components: one main relief valve (4), one priority reducing valve (5), one manual modulation valve (3), wiring harness (2), eight solenoid valves (7) and eight modulating reducing valves (6)

Main Relief Valve

Illustration 3

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(4) Main relief valve (8) Spool (9) Passage to transmission oil cooler (10) Orifice (11) Slug (12) Adjustment screw and locknut (13) Spring

The main relief valve is located in the top front quadrant of the inside valve body.

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Main relief valve (4) provides a restriction in the flow that sets the outlet pressure of the transmission pump. The oil that bypasses the main relief valve flows to transmission oil cooler line (9) . The main relief valve (4) has a slug (11) that is connected to the outlet flow by orifice (10) that is contained in spool (8). Slug (11) creates a reaction chamber. Oil in the reaction chamber acts against a spring in order to set the pressure. Spring (13) has an external adjustment screw and a locknut (12) that varies the valve pressure setting per turn.

Priority Reducing Valve

Illustration 4

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(4) Main relief valve (5) Priority reducing valve (14) Spool (15) Passage (16) Orifice (17) Slug (18) Springs

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The priority reducing valve is located at the top rear quadrant of the inside valve body. Priority reducing valve (5) reduces the supply pressure through passage (15) to the selector valves and solenoids. The priority reducing valve also provides priority to the selector valves and to the solenoids that are over the fill for the transmission clutch or over the modulation for the transmission clutch. The priority reducing valve (5) receives oil in parallel to main relief valve (4). Slug (17) provides a reaction chamber that is connected to the pump supply flow from the solenoid in passage (15) by orifice (16). The oil is contained in spool (14) and balances against the force of springs (18) in order to set the pressure.

Manual Modulation Valve (Inching Valve)

Illustration 5

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(3) Manual modulation valve (19) Connection for Push-Pull cable (20) Stop (21) Plunger (22) Piston (23) Springs (24) Spool (25) Slug (26) Adapter (27) Port for temperature sensor

The manual modulation valve is located in the uppermost portion of the outermost valve body.

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Manual modulation valve (3) is connected to the pedal with a push-pull cable (19). The manual modulation valve disengages or the manual modulation valve reduces the power that is transmitted to the drive wheels. This is accomplished by reducing the supply pressure to the directional modulating reducing valves. Modulation valve (3) consists of plunger (21), stop (20), piston (22), spool (24), springs (23), and slug (25). In order to have full pressure at the direction clutches, the transmission modulator control (pedal) must not be activated.

Illustration 6

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Location of the transmission modulator control (pedal)

Depressing the pedal reduces the supply pressure to the modulating reducing valve for the direction clutch. The pedal is located in the cab. Fully depressing the pedal reduces supply pressure to 0 kPa (0 psi). Slowly releasing the pedal allows supply pressure to gradually increase following pedal movement to approximately 755 kPa (110 psi). Once the pressure reaches 755 kPa (110 psi), the pressure automatically modulates to a minimum of 2085 kPa (300 psi) after approximately 0.2 seconds. Temperature sensor (27) is mounted into an adapter (26) in the manual modulation valve. Temperature sensor (27) monitors the oil temperature of the drive train.

Modulation Reducing Valve

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Illustration 7

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(7) Solenoid (28) Selector spool (29) Decay orifice (30) Load piston (31) Modulation orifice (32) Reducing spool (33) Slug (34) Springs

There are eight modulation reducing valves. Four of the modulation reducing valves are located in each valve body. These four provide individual pressure control for the clutch. The modulation reducing valve consists of selector spool (28), load piston (30), reducing spool (32), slug (33), modulation orifice (31), decay orifice (29) and springs (34). Each valve provides a unique pressure for each transmission clutch through different combinations of the springs and the orifices. To pressurize a transmission clutch, solenoid (7) is energized with a 24 volt signal from the electronic control module (ECM). The ECM is activated by the transmission shift lever. This causes selector spool (28) to move toward the center of the valve. This causes load piston (30) and reducing spool (32) to move away from the center of the valve. This will allow oil from the main relief valve to pass across the reducing valve in order to fill the clutch.

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When the clutch is full of oil, the oil flows through modulation orifice (31) that is contained in reducing spool (32). This moves load piston (30) toward the selector spool (28), compressing the modulation spring (34) and causing the transmission clutch pressure to gradually rise. In order to disengage the transmission clutch, the solenoid is de-energized. This allows selector spool (28) to move away from the center of the valve. The selector spool connects the load piston cavity in order to drain through decay orifice (29) that is contained in the valve body. This will gradually reduce the clutch pressure.

Solenoid Valves

Illustration 8

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(7a) Solenoid (7b) Solenoid (7c) Solenoid (7d) Solenoid (7e) Solenoid (7f) Solenoid (7g) Solenoid

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(7h) Solenoid (35) Speed selector spool (36) Speed range selector spool (37) Direction selector spool

Solenoid valves (7) connect pressurized oil from the priority reducing valve to the corresponding selector spool. The solenoid valves are 24 volt ON/OFF poppet type valves. These poppet type valves are activated. Table 1 Gear

Solenoids

Clutches

8-F

(B), (D), (G)

(1), (8), (5)

7-F

(B), (D), (E)

(1), (8), (4)

6-F

(C), (D), (E)

(2), (8), (4)

5-F

(B), (D), (F)

(1), (8), (6)

4-F

(B), (G), (H)

(1), (5), (7)

3-F

(C), (G), (H)

(2), (5), (7)

2-F

(C), (E), (H)

(2), (4), (7)

1-F

(B), (F), (H)

(1), (6), (7)

N

(D), (G)

(8), (5)

P

(D), (G)

(8), (5)

1-R

(A), (F), (H)

(3), (6), (7)

2-R

(A), (E), (H)

(3), (4), (7)

3-R

(A), (G), (H)

(3), (5), (7)

4-R

(A), (D), (F)

(3), (8), (6)

5-R

(A), (D), (E)

(3), (8), (4)

6-R

(A), (D), (G)

(3), (8), (5)

Speed Range Selector Spools Speed range selector spools (36) trigger the beginning of modulation. Speed range selector spools (36) also trigger the beginning of the decrease of the clutch pressure. The speed range selector spool also prevents the application of two speed range gears at a time. Energizing solenoid (7h) causes

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speed range selector spool (36) to move toward the center of the valve. This blocks the flow of oil to disengaged solenoid (7d). Also, this drains the supply port of disengaged solenoid (7d) .

Direction Selector Spools The direction selector spools are located in the front center region of the outer valve body. The direction selector spools are part of clutch stations (A), (B), and (C) . Direction selector spools (37) trigger the beginning of the modulation or the beginning of the decrease in clutch pressure. The direction selector spools also prevent the application of two direction clutches at a time. Energizing solenoid (7b) causes direction selector spool (37) to move toward the center of the valve. This blocks the flow of oil to disengaged solenoid (7a) and (7c). Also, this drains the supply port of disengaged solenoid (7a) and (7c) .

Speed Selector Spools The speed selector spools that are located in the front center region of the inner valve body are part of clutch stations (E), (F), and (G) . Speed selector spools (35) trigger the beginning of modulation or the beginning of the decrease in clutch pressure. The speed clutch selector spools also prevent the application of two speed clutches at a time. Energizing solenoid (7f) causes speed selector spool (35) to move toward the center of the valve. This blocks the flow of oil to disengaged solenoids (7e) and (7g). Also, this drains the supply port of disengaged solenoids (7e) and (7g) .

Manifold Ports for the Transmission Control Valve

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Illustration 9

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(38) Passage for clutch 2 (39) Lubrication (40) Elevated drain (41) Passage from the hydraulic pump (42) Passage to the oil cooler (43) Drain (44) Passage for clutch 8 (45) Clutch 7 at station (H) (46) Clutch 5 at station (G)

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(47) Clutch 6 at station (F) (48) Passage for clutch 4 (49) Passage for clutch 3 (50) Passage for clutch 1 (51) Pilot pressure

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