For 1990-2009 cars

# DIFFERENTIAL WEAR POSSIBLE CAUSES-THM125

FOR ANY CUSTOMER COMMENT OF RIGHT HAND AXLE LEAKS, GARAGE SHIFT CLUNKS , OR CLUNKS IN DRIVE WHILE ACCELERATING AND/OR DECELERATING USE THE FOLLOWING INFORMATION AS A DIAGNOSIS GUIDE. 1.A FIRST TIME RIGHT HAND AXLE LEAK WITHOUT ANY NOTICEABLE CLUNK WILL REQUIRE REPLACEMENT OF THE RIGHT HAND AXLE SEAL, PART NUMBER 8631156. A.AFTER REPLACING THE AXLE SEAL, CHECK THE AXLE BEARING JOURNALS - MICRO FINISH - FOR DAMAGE. USE CROCUS CLOTH TO POLISH THE JOURNALS IF NECESSARY. B.AFTER INSTALLING THE RIGHT HAND AXLE SEAL AND AXLE, PUSH UPWARD ON THE AXLE AND CHECK FOR ANY FURTHER LEAK. IF THE LEAK IS STILL PRESENT, THE DIFFERENTIAL ASSEMBLY, WHICH IS PART OF THE COMPLETE FINAL DRIVE ASSEMBLY, MUST BE REPLACED. FOR REPLACEMENT, FOLLOW THE SERVICE INFORMATION BELOW. 2.ANY RECURRING RIGHT HAND AXLE LEAKS, WITHOUT AN OBVIOUS CAUSE, WILL ALSO REQUIRE REPLACEMENT OF THE DIFFERENTIAL ASSEMBLY (FOLLOW SERVICE INFORMATION BELOW). 3.FOR A GARAGE SHIFT CLUNK WITH A RIGHT HAND AXLE LEAK, CHECK WHETHER THE CLUNK IS RESULTING FROM A HIGH ENGINE IDLE. (DO NOT CONFUSE A GARAGE SHIFT CLUNK WITH A HARSH GARAGE SHIFT-THE CLUNK IS A NOISE WHILE A HARSH SHIFT HAS AN AGGRESSIVE FEEL.) IF ADJUSTING THE ENGINE IDLE TO PROPER SPECIFICATION ELIMINATES THE CLUNK, REPLACE THE RIGHT HAND AXLE SEAL. IF ADJUSTING THE ENGINE IDLE DOES NOT CORRECT THE GARAGE SHIFT CLUNK OR IF THE ENGINE IDLE IS WITHIN SPECIFICATION, INSTALL AN OIL PRESSURE GAUGE ON THE TRANSMISSION AND CHECK FOR POSSIBLE HIGH LINE PRESSURE. IF A HIGH LINE PRESSURE IS FOUND DURING THIS CHECK, FOLLOW THE SERVICE MANUAL DIAGNOSIS SECTION TO REPAIR THE TRANSMISSION. IF THE OIL PRESSURE IS NORMAL, THE DIFFERENTIAL ASSEMBLY AND AXLE SEAL MUST BE REPLACED (FOLLOW SERVICE INFORMATION BELOW). 4.IF A CLUNK IS DETECTED WHILE ACCELERATING OR DECELERATING, EITHER WITH OR WITHOUT A GARAGE SHIFT CLUNK, ALONG WITH A RIGHT HAND AXLE LEAK, THE DIFFERENTIAL ASSEMBLY AND RIGHT HAND AXLE SEAL MUST BE REPLACED (FOLLOW SERVICE INFORMATION BELOW). A.IF THE CLUNK OCCURS ONLY ON A 3-2 COAST DOWN SHIFT, REPLACE ONLY THE INTERMEDIATE SERVO CUSHION SPRING AND RIGHT HAND AXLE SEAL. AFTER REASSEMBLING THE TRANSMISSION, FOLLOW STEP LB AGAIN. SERVICE INFORMATION IF THE DIFFERENTIAL ASSEMBLY MUST BE SERVICED, ORDER SERVICE PACKAGE NUMBER 8637907, WHICH WILL CONTAIN THE DIFFERENTIAL HOUSING, SPEEDOMETER DRIVE GEAR, FINAL DRIVE PINION PINS AND FINAL DRIVE PINION PIN RETAINER. ALSO, ORDER SERVICE PACKAGE NUMBER 8637919 WHICH WILL CONTAIN THE DIFFERENTIAL PINIONS, PIN AND SIDE GEARS. SERVICE PACKAGES 8637907 AND 8637919 MUST BE INSTALLED TOGETHER. ALSO, REPLACE THE RIGHT HAND AXLE SEAL. IF NECESSARY, THE FINAL DRIVE PINIONS CAN BE SERVICED USING THE CURRENT SERVICE PACKAGE NUMBER. NOTICE: GM PARTS DIVISION WILL NOTIFY DEALERS THROUGH SALES INFORMATION BULLETIN WHEN PARTS ARE AVAILABLE.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.