R2900G Load Haul Dump Power Train Caterpillar

The torque converter stall test is designed to test the engine, the torque converter, the drive train, and the brake system as a unit. The torque converter output is stalled while the engine is operated at full throttle. The speed of the engine at torque converter stall indicates whether the engine and the transmission are operating correctly under full load.

An engine speed lower or higher than the normal given speed indicates a problem in the engine or in the transmission. If testing shows correct engine performance, but the torque converter stall speed is not correct, the problem is in the torque converter or in the transmission.

The service brakes must be applied when tests are performed. Make sure that the service brakes are fully operational before you perform any tests. Make sure that the transmission oil is at the normal operating temperature when tests are performed.

The drive wheels must not turn during the torque converter stall test. Place the machine in an open area clear of personnel and obstructions. Engage the parking brake.

Show/hide table

Personal injury or death can result from sudden machine movement. Sudden movement of the machine can cause injury to persons on or near the machine. To prevent injury or death, make sure that the area around the machine is clear of personnel and obstructions before operating the machine.

Illustration 1	g01045124
(1) Tachometer (2) Display window for digital tachometer (3) Transmission autoshift control switch

1. Start the engine and apply the service brakes.

   Note: To ensure that the transmission oil does not overheat, do not keep the torque converter in a full stall condition for more than 30 seconds. After the torque converter is stalled, shift the transmission direction control to the NEUTRAL position. Operate the engine at 1200 rpm to 1500 rpm in order to cool the oil.

2. Move transmission autoshift control switch (3) to the MANUAL position in order to prevent any unexpected shifts during the stall test.

3. Shift the transmission direction and speed control to the THIRD SPEED FORWARD position. Fully depress the accelerator pedal. Allow the engine rpm to stabilize. Then, observe tachometers (1) and (2).

The correct stall speed is 1970 ± 40 rpm at 120 °C (250 °F).

Stall speeds that are low indicate incorrect engine performance. Stall speeds that are high indicate incorrect transmission performance or incorrect performance of the torque converter. If you must repeat the test, keep the transmission in neutral and wait for 2 minutes between tests.

Reference: For additional information about troubleshooting the transmission and the torque converter, refer to Systems Operation, Testing and Adjusting, "Power Train Troubleshooting" for the machine that is being serviced.