GEAR GP-BEVEL & PINION 4762857 - Caterpillar

Symptom
The buildup time and the recovery time are excessive. The air compressor should be capable of raising the air system pressure from 586 kPa (85 psi) to 689 kPa (100 psi) in less than 40 seconds.Probable Cause
Dirty air filterInspect the air filter and replace the air filter, if necessary.
Restricted air induction lineInspect the air induction line for restrictions. Replace the air induction line, if necessary.
Restricted discharge line or discharge chamberInspect the discharge port of the air compressor and the discharge line of the air compressor for restrictions or carbon buildup. Check for proper cooling of the air compressor if carbon buildup is found. Replace any faulty sections of the discharge line, if necessary.
Slipping drive componentsCheck for faulty drive gears. Replace the air compressor if the drive gears are faulty.
Excessive leakage of the air systemTest for excessive leakage of the air system. Repair air leaks, if necessary. Build the pressure in the air system until the air system reaches the pressure for the governor cutout. Allow the air system pressure to stabilize for one minute. Read the dash gauge and record the system pressure. Wait for two minutes and read the dash gauge. Record the system pressure again. Subtract the second reading from the initial reading. Divide this figure by the number of reservoirs on your vehicle and trailer. Compare this figure with the values in Table 2.
Table 1
Type of Vehicle     Pressure Drop After 2 Minutes    
Tractor without Trailer    
14 kPa (2 psi)    
Tractor and One Trailer    
41 kPa (6 psi)    
Tractor and Two Trailers    
55 kPa (8 psi)    
Sticking unloader pistonCheck the operation of the unloading mechanism. Check the operation of the governor. Inspect the tubing and hoses that are connected to the governor. Check for restrictions. If the governor operates properly, the problem is with the unloading mechanism of the air compressor.
Faulty air compressorRepair the air compressor or replace the air compressor if none of the described conditions exist.