SENSOR GP-POS 1932548 - Caterpillar

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.
Specifications
Table 1
Transmission Charging Oil Pressure
Engine Speed Pressure
Low Idle (700 rpm) 2725 69 kPa (395 10 psi)
High Idle (2200 rpm) 3240 69 kPa (470 10 psi) Introduction
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.This test will show the following conditions if the conditions exist:
The gear pump is operating at the correct pressure
The main relief valve is correctly setRequired Tools
Illustration 1 g02571852
Tooling (A) 198-4240 Digital Pressure Indicator Gp
Table 2
Required Tools
Tool Item Qty Part No Description
A 198-4240 Digital Pressure Indicator Gp
A1 1 198-4234 Digital Indicator
A2 1 198-4237 Pressure Sensor Gp
(0 to 3,445 kPa (0 to 500 psi))
A3 1 198-4236 Adapter Cable As Test Preparation
Move the machine to a smooth horizontal location. Move away from any machines that are working and any personnel.
Move the transmission control to the P position. Fully raise the dump body of the truck.
Install the retaining pin for the dump body.
Stop the engine.
Permit only one operator on the machine. Either keep other personnel away from the machine, or keep other personnel in the sight of the operator.
Place blocks in front of the wheels and behind the wheels.
Illustration 2 g03328195
View of the top of the transmission on the 770G
(1) Main relief valve
(2) Pressure tap for the main relief valve
Illustration 3 g03328177
View of the top of the transmission on the 772G
(1) Main relief valve
(2) Pressure tap for the main relief valve
Connect tooling (A) onto pressure tap (2). Test Procedure
Start the engine and run the engine at the low idle rpm while the transmission is in NEUTRAL. The pressure on the gauge should be 2725 69 kPa (395 10 psi).
Increase the engine speed to high idle rpm. The pressure on the gauge should be 3240 69 kPa (470 10 psi).
When this test is complete, stop the engine and remove the test equipment. Adjustment Procedure
Illustration 4 g03328152
Main relief valve
(3) Adjustment screw Note: The main relief valve is located on the hydraulic control valve on the transmission.
Use adjustment screw (3) in order to achieve the correct pressure. Note: Turning adjustment screw (3) clockwise will increase the pump pressure. Turning adjustment screw (3) counterclockwise will decrease the pump pressure. One full rotation of adjustment screw (3) will adjust the pressure approximately 158 kPa (23 psi).
Recheck the pressure after each adjustment. Problem: The oil pressure is too low.
Probable Cause
Failure of the gear pump of the power train
The setting of main relief valve (3) is too low. Adjust the relief valve to the low idle setting.Problem: The oil pressure is too high.
Probable