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| Illustration 1 | g06086699 |
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Location of the Modulating Valves (Transmission Clutch Solenoid) (1) Number 1 modulating valve - clutch solenoid (Reverse) (2) Number 2 modulating valve - clutch solenoid (Forward) (3) Number 3 modulating valve - clutch solenoid (Fourth Speed) (4) Number 4 modulating valve - clutch solenoid (Third Speed) (5) Number 5 modulating valve - clutch solenoid (Second Speed) (6) Number 6 modulating valve - clutch solenoid (First Speed) | |
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| Illustration 2 | g00562502 |
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Modulating Valve (Transmission Clutch Solenoid) | |
The six modulating valves (clutch solenoid) are mounted on the top of the transmission. There is one clutch solenoid modulating valve for each of the six transmission clutches.
The transmission clutch modulating valves are outputs of the Power Train Electronic Control Module (ECM). The clutch solenoid modulating valves are proportional solenoid valves. The clutch solenoid 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 when the operator selects a speed the Power Train ECM sends a pulse width modulated signal (PWM) to vary the current to the clutch solenoid. 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 clutch solenoid 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 clutch solenoid modulating valve, the oil pressure in the clutch is at the maximum. When no current is sent to the clutch solenoid modulating valve, the oil pressure in the clutch should be zero.
The Power Train ECM will activate the transmission clutch solenoid modulating valve that is selected by the operator. Clutch solenoid modulating valves (1) and (2) supply oil to the direction clutches. Clutch solenoid 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 clutch solenoid modulating valve (3) is energized. When the transmission is shifted to neutral, the direction clutch solenoid and the speed clutch solenoid are de-energized. No. 3 clutch solenoid (3) is then energized.
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| Illustration 3 | g06087229 |
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(1) Ball
(2) Chamber (3) Orifice (4) Test port (5) Valve spool (6) Passage (7) Spring (8) Chamber (9) Solenoid (10) Pin (11) Drain orifice (12) Tank passage (13) Passage to the clutch (14) Passage (15) Pump passage (A) Pump oil (B) Return oil | |
When the Power Train ECM requires a clutch to be disengaged, there is no flow of electric current to the solenoid.
Pump oil (A) flows into the valve body from pump oil passage (15). Oil then flows into oil passage (14), through orifice (3) and into chamber (2). Since there is no signal that is sent to solenoid (9), pin (10) cannot hold ball (1) against orifice (11). The flow of the oil passes through orifice (11) past ball (1) to the tank passage (12). The oil in tank passage (12) becomes return oil (B).
Spring (7) holds valve spool (5) to the left. When valve spool (5) is shifted to the left, the oil in the clutch oil passage (13) flows to tank passage (12). When the oil in clutch oil passage (13) is vented to the tank, the clutch cannot be engaged. The oil in pump oil passage (15) is blocked from entering clutch oil passage (13).
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| Illustration 4 | g06087232 |
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(1) Ball
(2) Chamber (3) Orifice (4) Test port (5) Valve spool (6) Passage (7) Spring (8) Chamber (9) Solenoid (10) Pin (11) Drain orifice (12) Tank passage (13) Passage to the clutch (14) Passage (15) Pump passage (A) Pump oil (B) Return oil (C) First pressure reduction (D) Reduced pilot oil pressure | |
When the Power Train ECM requires a clutch to be engaged, a signal is sent to the solenoid (9). The strength of the signal is proportional to the desired clutch pressure.
When the signal is sent to the solenoid, pin (10) moves to the right and pin (10) forces ball (1) toward orifice (3). When ball (1) moves toward orifice (3), the flow of return oil (B) into tank passage (12) is restricted. Pressure in chamber (2) increases and the oil becomes reduced pilot oil pressure (D). The pressure moves valve spool (5) to the right against the force of spring (7).
When valve spool (5) moves to the right, pump oil (C) in pump passage (15) enters clutch oil passage (13). The valve spool blocks the flow of oil from clutch oil passage (13) to tank passage (12). The clutch pressure will increase due to the flow of reduced pressure oil (C) into clutch oil passage (13). The oil in clutch oil passage (13) also flows through passage (6) into chamber (8).
Initially, the Power Train ECM sends a high signal to the solenoid to fill the clutch with oil quickly. Then, a reduced signal is sent to the solenoid to allow the clutch to engage smoothly.
Once the clutch engages, the Power Train ECM begins to increase the signal to solenoid (9) to increase engagement of the clutch. When the signal to solenoid (9) increases, pin (10) moves to the right. Pin (10) pushes ball (1) toward orifice (3) and ball (1) restricts the flow of oil to tank passage (12). Oil pressure in chamber (2) will rise and valve spool (5) will move to the right. The valve spool position causes the clutch pressure to increase.
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| Illustration 5 | g06087237 |
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(1) Ball
(2) Chamber (3) Orifice (4) Test port (5) Valve spool (6) Passage (7) Spring (8) Chamber (9) Solenoid (10) Pin (11) Drain orifice (12) Tank passage (13) Passage to the clutch (14) Passage (15) Pump passage (A) Pump oil (B) Return oil (C) Pilot oil | |
When the clutch is fully engaged, the Power Train ECM sends the maximum specified signal to solenoid (9) to keep the clutch fully engaged.
The signal that is sent to solenoid (9) moves pin (10) and ball (1) to the right. The position further restricts the flow of return oil (B) from clutch oil passage (13) to tank passage (12). The pressure in chamber (2) increases and the oil becomes pilot oil (C). Valve spool (5) moves further to the right. The pump oil (A) from pump passage (14) flows to clutch oil passage (13) and the clutch will fully engage.
Once the clutch is fully engaged, pump oil (A) in chamber (2) and the combined pressure of oil in chamber (8) and spring (7) will equalize. The equalized pressure will cause valve spool (5) to move to the left to a balanced position.
In the balanced position, the flow of oil from pump oil passage (15) to clutch oil passage (13) maintains the desired clutch pressure. In the balanced position, oil flows to the clutch 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 Power Train 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 Power Train ECM.
Note: The main relief valve will control the maximum amount of clutch pressure for all the modulating valves. The pump supply pressure and the clutch pressure will be equal when the clutch is fully engaged.