777E and 777F Off-Highway Truck Power Train Caterpillar

Illustration 1	g01263532
Transmission hydraulic control valve (1) Transmission lubrication relief valve

Note: Make sure that the filters and the screens are clean before you test any pressures. Make sure that the oil is at operating temperature before you perform this test.

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Personal injury or death can result from sudden machine movement. Sudden movement of the machine or release of air pressure or oil pressure can cause injury to persons on or near the machine. To help prevent possible injury before testing and adjusting any air system or hydraulic system, perform the procedure in the Testing and Adjusting, "General Information" section.

This test will show the following conditions if the conditions exist:

• The oil pressure to the transmission lubrication circuit is good.

• The relief valve for the transmission oil cooler is closed.

Procedure

Illustration 2	g01263534
(2) Pressure tap for the lubrication of the transmission

1. Connect Tooling (A) to the nipple at pressure tap (2).

2. Place the transmission in PARK. Start the engine. Run the engine at the LOW idle rpm. The pressure on the gauge must be a minimum of 4 kPa (0.5 psi).

3. Run the engine at the HIGH idle rpm while the transmission is in PARK. The pressure on the gauge must be 110 ± 30 kPa (16 ± 4 psi).

4. When this test is complete, run the engine at the LOW idle rpm. Stop the engine and remove the test equipment.

Problem

The pressure of the pump section for charging the transmission is correct and the transmission lubrication pressure is too low.

Probable Cause

• The relief valve for the transmission lubrication is open.

• There is too much leakage in the transmission lubrication circuit.

Problem

The oil gets too hot during normal operation.

Probable Cause

• There is to much oil in the transmission case. Perform the check in the Power Train Testing and Adjusting, "Transmission troubleshooting".