INFO. ON REAR AXLE LUBRICANT COMPATIBILITY. Chevrolet Chevy P12 Chassis 1998

SUBJECT: INFORMATION ON REAR AXLE LUBRICANT COMPATIBILITY

MODELS: 1988-98 CHEVROLET AND GMC C/K, G, P10, 20, 30 SERIES MODELS

THIS BULLETIN IS TO INFORM DEALERS ABOUT THE COMPATIBILITY OF THE NEW FUEL EFFICIENT SAE 75W-90 SYNTHETIC AXLE LUBRICANT, P/N 12378261, WITH CURRENT AND PAST MODEL SEALS, AND WITH THE NON-SYNTHETIC AXLE LUBRICANT, P/N 1052271, FOR THE REAR AXLES ON THE ABOVE LIGHT-DUTY TRUCKS.

TESTING HAS SHOWN THAT THE NEW SYNTHETIC LUBRICANT MAY CHEMICALLY ATTACK THE RTV (ROOM TEMPERATURE VULCANIZING) SEALANT. USE ONLY THE NON-SYNTHETIC LUBRICANT, P/N 1052271, IN AXLES USING RTV SEALANT.

AMERICAN AXLE AND MANUFACTURING (A.A.M) HAS APPROVED THE USE OF THE NEW FUEL EFFICIENT SAE 75W-90 SYNTHETIC AXLE LUBRICANT FOR REAR AXLES WITH THE FOLLOWING RESTRICTIONS:

- ALL 8.6 INCH AXLES ARE COMPATIBLE AS ORIGINALLY BUILT.

- 9.5 INCH AXLES ON VEHICLES BUILT PRIOR TO MID FEBRUARY 1998* ARE NOT COMPATIBLE BECAUSE RTV SEALANT IS USED ON THE COVER PANS.

*ON VEHICLES BUILT AFTER MID FEBRUARY 1998, EQUIPPED WITH 9.5 INCH REAR AXLES, SYNTHETIC GEAR LUBRICANT, P/N 12378261, CAN BE USED BECAUSE OF A NEW GASKET MATERIAL. OTHER MID FEBRUARY CHANGES TO THE 9.5 INCH REAR AXLES INCLUDE A NEW COVER PAN AND COVER PAN FASTENERS COMMON TO OTHER AXLES.

IMPORTANT: THE NEW COVER PAN IS NOT RETROFITTABLE TO THE HOUSING OF 9.5 INCH AXLES ON VEHICLES BUILT PRIOR TO MID FEBRUARY 1998. A NEW RETROFIT KIT IS AVAILABLE THAT WILL ENABLE THE USE OF SYNTHETIC LUBRICANT.

- ALL 10.5 INCH AXLES ARE COMPATIBLE IF THE AXLE SHAFT SEAL IS REPLACED WITH P/N 327739 GASKET WHEN CHANGING TO SYNTHETIC LUBRICANT. AS OF MARCH 3, 1998, AN RTV SEALER IS STILL USED FOR THE REAR AXLE SHAFT SEAL ON THE 10.5 INCH AXLE.

IMPORTANT: YOU DO NOT NEED TO WASH/RINSE ANY NON-SYNTHETIC LUBRICANT FROM THE AXLE CAVITY WHEN CHANGING OVER TO A SYNTHETIC LUBRICANT. HOWEVER, YOU SHOULD REMOVE DEBRIS FROM THE MAGNET AND THE BOTTOM OF THE AXLE CAVITY WHENEVER THE AXLE FLUID IS CHANGED.

ON LIGHT DUTY TRUCK MODELS EQUIPPED WITH LOCKING DIFFERENTIALS, DO NOT USE A LIMITED SLIP ADDITIVE. IT IS NOT RECOMMENDED AND SHOULD NOT BE USED.

PARTS INFORMATION:

P/N DESCRIPTION QTY

327739 GASKET, AXLE SHAFT SEAL 1

12378261 FUEL EFFICIENT SAE 75W-90 1 SYNTHETIC AXLE LUBRICANT

1052271 NON-SYNTHETIC LUBRICANT 1

12471310 KIT, 9.5 INCH AXLE COVER PAN 1

PARTS ARE CURRENTLY AVAILABLE FROM GMSPO.

FIGURES: 00 ATTACHMENTS: 00

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.