770G and 772G Off-Highway Truck (OEM) Hydraulic and Braking System: Relief Valve (Brake Oil Cooler) - Test and Adjust & Limit Switch (Truck Body Up) - Adjust

Relief Valve (Brake Oil Cooler) - Test and Adjust

In Chassis Test and Adjust Procedure

Table 1

Required Tools
Part Number	Description	Required Amount
198-4240	Digital Pressure Indicator	1
2J-5608	Cover	1
4J-0527	O-Ring Seal	1

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.

(1) Pressure tap on the pump

(2) Tube assembly(3) Brake oil cooler relief valve

Section view of brake oil cooler relief valve (3) (3) Brake oil cooler relief valve(4) Shims

1. Connect 198-4240 Digital Pressure Indicator to pressure tap (1) .

2. Start the engine. Run the engine at low idle.

3. Raise the dump body.

4. Move the control lever for the hoist control to the Float.

Typical



5. When the display indicates the dump body has entered SNUB, look at the pressure gauge. The pressure reading should be less than 1725 kPa (250 psi).Note: The Snub position can be read on the ET screen, the Messenger screen, or the Advisor screen.
   Note: The pressure reading was the result of bench testing the relief valve at a flow rate of 38 L/min (10 US gpm). The flow rate of the pump at low idle is 167 L/min (44 US gpm). The resulting pressure may be higher than the value that is provided.

6. The pressure can be lowered in ET by using the "hoist Lower adjustment". See Special Instruction, REHS5093, "Assembly Procedure for the 772G Off-Highway Trucks", "Adjustment for Hoist Lower Value".Note: Special Instruction, REHS5093, "Assembly Procedure for the 772G Off-Highway Trucks", "Adjustment for Hoist Lower Value" is not yet complete.

7. Stop the engine.

8. Remove the test equipment.

Bench Test and Adjustment

Table 2

Shims For Adjusting The Relief Valve Pressure Setting
Part Number	Thickness	Pressure Change
8B-4624	0.81 mm (0.032 inch)	30 kPa (4 psi)

Problem: The pressure is less than 586 ± 14 kPa (85 ± 2 psi).

Probable Cause

• Brake oil cooler relief valve (3) is stuck open.
• Brake oil cooler relief valve (3) is set too low. Add shims (4) . Refer to Table 2.

Problem: The pressure is greater than 586 ± 14 kPa (85 ± 2 psi).

Probable Cause

• Brake oil cooler relief valve (3) is set too high. Remove shims (4) . Refer to Table 2.

Limit Switch (Truck Body Up) - Adjust

Note: Before adjusting truck body up limit switch (2), the pad assemblies and the shims must be installed Systems Operation/Testing and Adjusting, "Pad Assembly (Truck Body) - Install and Adjust" for the proper installation of the pad assemblies.

Truck body in the UP position (1) Lever (2) Limit Switch (Truck Body Up)(A) 45 degrees



1. Raise the truck body and install the proper safety device in order to secure the truck body in the UP position. Adjust lever (1) initially to a 45 degree angle in the upward direction.

Truck body in the DOWN position (1) Lever (2) Limit Switch (Truck Body Up)(3) Truck body position plate



2. Remove the safety device and lower the truck body into the DOWN position. Adjust truck body up limit switch (2) forward or rearward in order to position lever (1) in contact with truck body position plate (3). Truck body position plate (3) should contact lever (1) as the truck body moves into the down position.

3. In order to adjust the snub position of the truck body to approximately 200 to 300 mm (8 to 12 inch), cycle the truck body and observe the SNUB position. If the truck body reaches the SNUB position too early, move lever (1) downward by one notch. If the truck body reaches the SNUB position too late, move lever (1) upward by one notch.

4. Repeat Step 3 until the desired SNUB position of the truck body is obtained.

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