GEAR 5I5789 - Caterpillar

Personal injury or death can result from sudden machine movement.Sudden movement of the machine or release of oil pressure can cause injury to persons on or near the machine.To help prevent possible injury or death, refer to the information in Testing and Adjusting, "Machine Preparation for Troubleshooting".
Start the engine. Operate the engine at high idle.
Move the hoist control to the RAISE position. Hold the hoist control in the RAISE position for five seconds after the dump body is fully raised. Then, lower the dump body all the way to the truck frame.
Repeat Step 2 until the temperature of the hydraulic oil is 38 °C (100 °F).Cycle Times for Hoist Cylinders
Lower the dump body to the truck frame.
Operate the engine at high idle.
Raise the dump body to the fully raised position. Use a stopwatch to measure the required time.The required time for full extension of the hoist cylinders is 16 seconds.Cylinder Drift
Note: Perform this test with an empty dump body and hydraulic oil above 38°C (100°F).
Move the hoist control to the RAISE position.
When the hoist cylinders are extended by 305 mm (12 inch), move the hoist control to the HOLD position.
The dump body will push the cylinder rod 6.35 mm (0.250 inch) onto the hoist cylinders. Use a stopwatch and record the required time.The acceptable time for cylinder drift is relative to the temperature of the hydraulic oil in the hoist cylinders. See Table 1 for the acceptable time.
Table 1
Acceptable Cylinder Drift    
Minutes     Oil Temperature     Cylinder Drift    
7.0    
38° to 48°C (100° to 119°F)    
6.35 mm (0.250 inch)    
4.1    
49° to 64°C (120° to 149°F)    
6.35 mm (0.250 inch)    
3.0    
65 °C (150 °F)    
6.35 mm (0.250 inch)    Excessive cylinder drift can be caused by the following conditions:
Leaks in the lines between the hydraulic oil tank and the hoist cylinders
Worn control valve spool
Worn seals in the hoist cylinders