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| Illustration 1 | g00907797 |
Location of the Modulating Valves (Transmission Clutch) (1) Number 1 clutch modulating valve (Reverse) (2) Number 2 clutch modulating valve (Forward) (3) Number 3 clutch modulating valve (Fourth Speed) (4) Number 4 clutch modulating valve (Third Speed) (5) Number 5 clutch modulating valve (Second Speed) (6) Number 6 clutch modulating valve (First Speed) | |
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| Illustration 2 | g00879095 |
Modulating Valve (Transmission Clutch) | |
The transmission clutch solenoid modulating valves are mounted on the top of the transmission under the cab. There is one modulating valve for each of the six transmission clutches.
The modulating valves are outputs of the power train electronic control module (ECM). The transmission clutch solenoid modulating valves are proportional solenoid valves. The modulating valves are used by the power train ECM to directly modulate the oil pressure that is sent to each individual clutch. When the operator selects a direction or selects a speed, the power train ECM sends a pulse width modulated signal (PWM). The (PWM) signal will vary the current to the solenoid for the clutch. The distance that is traveled by the solenoid plunger (valve) is proportional to the electrical current of the solenoid. The position of the solenoid plunger (valve) controls the oil pressure of the selected clutch. The amount of current that is sent to the modulating valve regulates the amount of oil pressure that is supplied to the selected clutch. When the power train ECM sends the maximum current to the modulating valve, the oil pressure in the clutch is at the maximum. When no current is sent to the modulating valve, the oil pressure in the clutch is at the minimum.
The power train ECM will activate the modulating valves that are selected by the operator. Modulating valves (1) and (2) supply oil to the direction clutches. Modulating valves (3) , (4) , (5) and (6) supply oil to the speed clutches. In order for the machine to move, one speed clutch solenoid and one direction clutch solenoid must be energized. When the transmission is in neutral, only one modulating valve (3) is energized. When the transmission is shifted to neutral, the direction clutch solenoid is de-energized and the present speed clutch solenoid is energized.
The modulating valves have a connector with two contacts. One contact receives power from the corresponding connector contact of the power train ECM (J1-48, J1-49, J1-52, J1-58, J1-59 and J1-62). The other contact of all the modulating valves join. The contacts return power to connector contact J1-50, J1-60, and J1-61 of the power train ECM.
Note: The solenoid coils are designed not to be operated at 24 DCV directly. The power train ECM sends a 24 V PWM signal at a duty cycle which provides about 12 V to the solenoid coils. Do not energize the solenoid coils with 24 DCV (+battery). The life of the solenoid coils will be drastically reduced if the solenoid coils are energized with 24 DCV (+battery). If the solenoid coils must be energized by a source that is different from the power train ECM, use 12 DCV.
Neutral
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| Illustration 3 | g01103086 |
(1) Ball (2) Orifice (3) Test port (4) Valve spool (5) Spring (6) Pump passage (7) Passage (8) Passage to the clutch (9) Tank passage (10) Drain orifice (11) Pin (12) Solenoid (13) Chamber (14) Passage (15) Chamber (16) Pump oil (17) Return oil | |
When the machine ECM requires a clutch to be disengaged, there is no flow of electric current to the solenoid.
Pump oil (16) flows into the valve body from pump oil passage (6) . Oil then flows into oil passage (7) , through orifice (2) and into chamber (13) . Since there is no signal that is sent to solenoid (12) , pin (11) cannot hold ball (1) against orifice (10) . The flow of the oil passes through orifice (10) past ball (1) to the tank passage (9) . The oil in tank passage (9) becomes return oil (17) .
Spring (5) holds valve spool (4) to the left. When valve spool (4) is shifted to the left, the oil in the clutch oil passage (8) flows to tank passage (9) . When the oil in clutch oil passage (8) is vented to the tank, the clutch cannot be engaged. The oil in pump oil passage (6) is blocked from entering clutch oil passage (8) .
Less Than Maximum Signal
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| Illustration 4 | g01103176 |
(1) Ball (2) Orifice (3) Test port (4) Valve spool (5) Spring (6) Pump passage (7) Passage (8) Passage to the clutch (9) Tank passage (10) Drain orifice (11) Pin (12) Solenoid (13) Chamber (14) Passage (15) Chamber (16) Pump oil (17) First pressure reduction (18) Return oil (19) Reduced pilot oil pressure | |
When the machine ECM requires a clutch to be engaged, a signal is sent to the solenoid (12) . The strength of the signal is proportional to the desired clutch pressure.
When the signal is sent to the solenoid, pin (11) moves to the right and pin (11) forces ball (1) toward orifice (2) . When ball (1) moves toward orifice (2) , the flow of return oil (18) into tank passage (9) is restricted. Pressure in chamber (13) increases and the oil becomes reduced pilot oil pressure (19) . The pressure moves valve spool (4) to the right against the force of spring (5) .
When valve spool (4) moves to the right, pump oil (16) in pump passage (6) enters clutch oil passage (8) . The valve spool blocks the flow of oil from clutch oil passage (8) to tank passage (9) . The clutch pressure will increase due to the flow of reduced pressure oil (17) into clutch oil passage (8) . The oil in clutch oil passage (8) also flows through passage (14) into chamber (15) .
Initially, the machine ECM sends a high signal to the solenoid in order to fill the clutch with oil quickly. Then, a reduced signal is sent to the solenoid in order to allow the clutch to engage smoothly.
Once the clutch engages, the machine ECM begins to increase the signal to solenoid (12) in order to increase engagement of the clutch. When the signal to solenoid (12) increases, pin (11) moves to the right. Pin (11) pushes ball (1) toward orifice (2) and ball (1) restricts the flow of oil to tank passage (9) . Oil pressure in chamber (13) will rise and valve spool (4) will move to the right. The valve spool position causes the clutch pressure to increase.
Maximum Signal
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| Illustration 5 | g01103160 |
(1) Ball (2) Orifice (3) Test port (4) Valve spool (5) Spring (6) Pump passage (7) Passage (8) Passage to the clutch (9) Tank passage (10) Drain orifice (11) Pin (12) Solenoid (13) Chamber (14) Passage (15) Chamber (16) Pump oil (17) Return oil (18) Pilot oil | |
When the clutch is fully engaged, the machine ECM sends the maximum specified signal to solenoid (12) in order to keep the clutch fully engaged.
The signal that is sent to solenoid (12) moves pin (11) and ball (1) to the right. The position further restricts the flow of return oil (17) from clutch oil passage (8) to tank passage (9) . The pressure in chamber (13) increases and the oil becomes pilot oil (18) . The valve spool (4) moves further to the right. The pump oil (16) from pump passage (7) flows to clutch oil passage (8) and the clutch will fully engage.
Once the clutch is fully engaged, pump oil (16) in chamber (13) and the combined pressure of oil in chamber (15) and spring (5) will equalize. The equalized pressure will cause valve spool (4) to move to the left to a balanced position.
In the balanced position, the flow of oil from pump oil passage (6) to clutch oil passage (8) maintains the desired clutch pressure. In the balanced position, oil flows to the clutch in order to compensate for internal leakage in the clutch.
Note: The modulating valves control the engaging and the disengaging of the clutches. This valve is not a simple on/off valve. The machine ECM varies the strength of the signal that is sent to the solenoid. The signal that is sent to the solenoid is programmed into the machine ECM.
Note: Since the main relief valve will control the maximum amount of clutch pressure for all of the modulating valves, the pump supply pressure and the clutch pressure will be equal when the clutch is fully engaged.
ReferenceFor information on troubleshooting the transmission, refer to the Service Manual module for Testing and Adjusting, "Transmission Troubleshooting" for the machine that is being serviced.
ReferenceFor information on calibrating the clutch solenoid modulating valves, refer to the Service Manual module for Testing and Adjusting, "Calibration" for the machine that is being serviced.
ReferenceFor more information on the power train electronic control module (ECM), refer to the Service Manual module for Systems Operation, "Electronic Control Module (Power Train)" for the machine that is being serviced.