SUPPORT AS 1785992 - Caterpillar

Torque Converter Lockup Clutch
Illustration 2 g01338040
Rear view of the torque converterThe torque converter lockup clutch and a solenoid valve (3) are mounted on the rear of the torque converter.The correct pressure for the torque converter lockup clutch is dependent upon the correct adjustment and the correct operation of the solenoid valve.The valve for the torque converter lockup clutch is controlled by a pilot oil supply that is controlled by the torque converter lockup clutch solenoid.To test the function of the solenoid valve for the torque converter lockup clutch, test the pressure of the pilot oil from the solenoid valve. If the pressure of the pilot oil from the torque converter lockup clutch solenoid is outside the specifications, there may be a fault with the supply of oil to the solenoid.Measure the main relief pressure for the transmission hydraulic control.If the main relief pressure for the transmission hydraulic control is correct, there is a problem with the torque converter lockup clutch solenoid.Testing the Torque Converter Lockup Clutch Solenoid
Ensure that the machine is parked on a level surface and that the parking brake control is engaged.
Move the key start switch to the ON position. Do not start the engine.
Raise the body.
Disconnect the wires from the upshift solenoid, the downshift solenoid and the torque converter lockup clutch solenoid.
Connect the harness from the downshift solenoid to the torque converter lockup clutch solenoid.
Use a tag wire to check that the solenoid coil is energized. If the tag wire is attracted to the solenoid coil, this indicates that the solenoid coil is energized. If the tag wire does not indicate that the solenoid coil is energized, the problem may be in the electrical circuit.
If the solenoid does not appear to function, disconnect the connector for the solenoid valve. Check the resistance of the windings of the coil in the solenoid. The resistance of the windings in the solenoid should be 32.6Ω 1.6Ω.If the resistance of the windings is outside the specifications replace the solenoid. If the solenoid coil is energized, the problem may lie with the solenoid cartridge. The problem could be a bent solenoid stem, a spring that is weak or broken, or a screen that is dirty or plugged.If the torque converter lockup clutch solenoid is functioning