SPRING 2588149 - Caterpillar

Illustration 2 g00562502
Transmission Clutch Solenoid Modulating Valve
The six clutch solenoid modulating valves are mounted on the top of the transmission under the cab. There is one clutch solenoid modulating valve for each of the six transmission clutches.The clutch solenoid 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) in order 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.The clutch solenoid modulating valves have a connector with two contacts. One contact receives power from the corresponding connector contact of the power train ECM (J1-11, J1-17, J2-1, J2-2, J2-7 , and J2-8). The other contact of all the solenoid valves join. The contacts return power to connector contact J1-7 and J2-3 of the power train ECM.Neutral
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