GASKET 1G1878 - Caterpillar

Probable Cause
Contamination of the hydraulic system oil
Insufficient pressure oil to the brakes
Transmission drag
Insufficient system pressure
Failed brake components
Brake control valve
Proportional solenoid valveRecommended Actions
Follow this procedure if the machine does not move or if the machine moves slowly.Contamination Of The Hydraulic System Oil
Determine that the symptom is active.If the symptom is intermittent, then a probable cause is oil contamination.
Complete this procedure only if the symptom is active.Results
ACTIVE: Proceed to "Insufficient Pressure Oil To The Brakes".
NOT ACTIVE: If the symptom is not active, oil contamination may be the problem. Change the power train oil. Change the oil filter element and clean the screens.
Stop.Insufficient Pressure Oil To The Brakes
Check the brake pressure.The brakes are engaged by spring force. The brakes are released by pressure oil which is sent from the brake control valve to the brakes. Therefore, insufficient pressure oil to the brakes is a probable cause of the symptom.Reference: Refer to Systems Operation/Testing and Adjusting, M0064234, "Brake Pressure - Test".Expected Results
The pressure is correct.Results
OKAY: The pressure is correct. Proceed to "Transmission Drag".
NOT OKAY: The pressure is not correct. Proceed to "Insufficient System Pressure".Transmission Drag
Reference: Refer to Systems Operation/Testing and Adjusting, M0064234, "Transmission Clutch Pressure - Test".Note: The procedure should be completed at low idle.
Place pressure gauges on all transmission clutches.
Operate the engine.
Disengage the parking brake.
Press down the service brake pedal to engage the brakes.
Shift through all the transmission speeds.
Check that the proper clutches engage for each gear.
Check that the clutches disengage properly for each gear. The clutch that is disengaged should have a pressure below 137 kPa (20 psi).Expected Results
The transmission clutches engage and the transmission clutches disengage properly.Results
OKAY: The engagement of the transmission clutches was eliminated as the source of the symptom. Since the brake pressure was correct, then the brake control valve was eliminated as the cause of the symptom. Therefore, the brake is the probable cause of the symptom. Proceed to "Failed Brake Components".
NOT OKAY: The transmission clutches do not engage properly.Proceed to “The Transmission Clutch Does Not Engage” in Troubleshooting, "Transmission Clutch" in this module.
NOT OKAY: The Transmission Clutch Is Engaged and the Clutch Does Not Release.Proceed to “The Transmission Clutch Is Engaged and the Clutch Does Not Release” in Troubleshooting, "Transmission Clutch" in this module.Insufficient System Pressure
Check the system pressure.Reference: Refer to Systems Operation/Testing and Adjusting, M0064234, "Relief Valve (Transmission) - Test and Adjust".Expected Results
The system pressure is correct.Results
OKAY: The system pressure is correct. The brake pressure is not correct. Inspect the brake control valve. Proceed to "Brake Control Valve".
NOT OKAY: The cause of the symptom may be the adjustment of the transmission relief valve. The transmission relief valve maintains the system pressure in the control section of the power train oil pump. Refer to Troubleshooting, "Power Train System Pressure Is Low" in this manual.Failed Brake Components
Check the brakes.The brake pressure is correct and the engagement of the transmission clutches is correct. Therefore, the brakes are the probable cause of the symptom.
Disassemble the brakes and check the following components of the brakes for failure:
Brake housing
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