777F Off-Highway Truck Hydraulic System Caterpillar

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Personal injury or death can result from machine movement. Place blocks in front of and behind the wheels to make sure the machine does not move while the parking brakes are disengaged.

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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.

1. Place the transmission control into the PARK position. Placing the transmission in PARK will engage the parking brakes.
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   Illustration 1	g01261840
   (1) Pressure tap for the rear slack adjuster.

2. Install a 8T-0857 Pressure Gauge ( 0 to 10000 kPa (0 to 1450 psi)) to pressure tap (1) on the rear slack adjuster.
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   Illustration 2	g01261917
   (2) Pressure tap on the front slack adjuster.

3. Install a 8T-0857 Pressure Gauge ( 0 to 10000 kPa (0 to 1450 psi)) to pressure tap (2) on the front slack adjuster.

4. Start the engine. Operate the engine at low idle.

5. Move the retarder control lever to the full ON position. The following pressures should be indicated:

   • The oil pressure at the rear slack adjuster should be between 4274.75 kPa (620 psi) to 5653.7 kPa (820 psi).

   • Oil pressure at the front slack adjuster should be between 6205.3 kPa (900 psi) to 8480.6 kPa (1230 psi).

6. Move the retarder control lever to the OFF position. Apply the service brake. The following pressures should be indicated:

   • Oil pressure at the rear slack adjuster should be 6067 ± 345 kPa (880 ± 50 psi).

   • Oil pressure at the front slack adjuster should be 6946.5 ± 741.0 kPa (1007.5 ± 107.5 psi).

7. Stop the engine.

Note: Perform the Hydraulic SystemSystems Operation/Testing and Adjusting, "Slack Adjuster - Test and Adjust" in order to determine the pressure at each wheel.

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

Note: Make sure that you remove all air from the hydraulic brake system. See the Testing and Adjusting, "Brake System Air - Purge" for the procedure.