CAMPAIGN PREMATURE REAR WHEEL SKID BRAKE SHOES

DEFECT INVOLVED A DEFECT WHICH RELATES TO MOTOR VEHICLE SAFETY EXISTS WITH RESPECT TO ALL 1980 "X" BODY VEHICLES EQUIPPED WITH MANUAL TRANSMISSIONS AND CERTAIN EARLY 1980 "X" BODY VEHICLES EQUIPPED WITH AUTOMATIC TRANSMISSIONS. SPECIFICALLY, THE NHTSA CONCLUDED THAT THESE VEHICLES MAY BE SUBJECT TO FAILURE IN BRAKING PERFORMANCE. DEALER ACTION BASED ON THIS INITIAL DETERMINATION, DEALERS ARE TO REPLACE THE REAR BRAKE SHOES ON THESE VEHICLES WITH REPLACEMENT PARTS WHICH UTILIZE A LINING MATERIAL WHICH WILL GREATLY REDUCE THE LIKELIHOOD OF PREMATURE REAR WHEEL SKID. VEHICLES WITH MANUAL TRANSMISSION WILL HAVE NEW FRONT AND REAR PARKING BRAKE CABLES INSTALLED. THESE CABLE REPLACEMENTS ARE NECESSARY TO ENSURE MEETING PARKING BRAKE PERFORMANCE REQUIREMENTS WHICH APPLY TO MANUAL TRANSMISSION EQUIPPED VEHICLES. WITH A MANUAL TRANSMISSION VEHICLE THESE PARKING REQUIREMENTS MUST BE MET WITH THE PARKING BRAKE ONLY WHILE THE TRANSMISSION IS IN NEUTRAL. WITH AN AUTOMATIC TRANSMISSION VEHICLE THE "PARK" POSITION MAY BE USED TOGETHER WITH THE PARKING BRAKE. ALSO, DEALERS ARE TO INSPECT AND SERVICE THE PARKING BRAKE SYSTEM OF ALL VEHICLES, AS DESCRIBED IN THE TECHNICAL PROCEDURES, TO ASSURE THAT THE PARKING BRAKE SYSTEM IS FUNCTIONING PROPERLY. IN ADDITION TO THE CAMPAIGN SERVICE DISCUSSED ABOVE DEALERS ARE ALSO TO INSPECT THE FRONT BRAKE SYSTEM AND PROVIDE REPLACEMENT OF PARTS NECESSARY TO PROVIDE UNIFORMITY OF THE ENTIRE BRAKE SYSTEM. THIS ADDITIONAL ACTION IS BEING OFFERED TO ASSURE CUSTOMER SATISFACTION WITH THE PERFORMANCE OF THE COMPLETE BRAKING SYSTEM. VEHICLES INVOLVED ALL 1980 "X" SERIES EQUIPPED WITH MANUAL TRANSMISSIONS. EARLY PRODUCTION 1980 "X" SERIES EQUIPPED WITH AUTOMATIC TRANSMISSIONS. CHECK THE C.R.I.S. SYSTEM TO DETERMINE IF A SPECIFIC VEHICLE IS INVOLVED IN THIS CAMPAIGN. PARTS INFORMATION THE PARTS FOR THIS CAMPAIGN ARE TO BE OBTAINED FROM WDDGM. - ONE REAR BRAKE SHOE AND LINING SET, P/N 12300194 IS REQUIRED FOR EACH VEHICLE INVOLVED. - THE FOLLOWING PARKING BRAKE CABLE KIT IS TO BE ORDERED FOR EACH MANUAL TRANSMISSION EQUIPPED VEHICLE WITH SERIAL NUMBERS FROM AW100000 UP TO AND INCLUDING AW290849 (WILLOW RUN) AND AT100000 UP TO AND INCLUDING AT166153 (TARRYTOWN). PARKING BRAKE CABLE KIT PART NO. 25518758. THIS KIT INCLUDES THE FOLLOWING PARTS: FRONT CABLE P/N 25518753 RIGHT REAR CABLE P/N 25518754 LEFT REAR CABLE P/N 25518755 THE FOLLOWING FRONT BRAKE SHOE AND LINING KITS ARE TO BE ORDERED AS REQUIRED. REFER TO INSPECTION PROCEDURE, PAGE 6 OF THIS BULLETIN: - VEHICLE EQUIPPED WITH POWER BRAKES - P/N 18010987 - VEHICLE EQUIPPED WITH MANUAL BRAKES - P/N 18010986 (REFER TO PAGE 4 FOR ORDERING INFORMATION.) BESIDES CONTAINING BOTH FRONT SHOE AND LININGS, THESE KITS CONTAIN THE CALIPER ATTACHING PARTS (MOUNTING BOLTS, SLEEVES, BUSHINGS AND SILICONE GREASE). IMPORTANT MANUAL BRAKE KIT ORDERING INFORMATION MOST VEHICLES INVOLVED IN THIS CAMPAIGN ARE EQUIPPED WITH POWER BRAKES; THEREFORE THE NUMBER OF FRONT KITS REQUIRED FOR MANUAL BRAKE VEHICLES SHOULD BE LIMITED. FOR YOUR INFORMATION THE APPROXIMATE PERCENT OF GENERAL MOTORS VEHICLES BY CAR DIVISION INVOLVED IN THIS PROGRAM WITH MANUAL BRAKES IS AS FOLLOWS: BUICK = 3% MANUAL BRAKES CHEVROLET = 21% MANUAL BRAKES PONTIAC = 19% MANUAL BRAKES OLDSMOBILE = 5% MANUAL BRAKES SO THAT PARTS WILL BE OBTAINED AS SOON AS POSSIBLE, THEY SHOULD BE ORDERED FROM WDDGM ON A C.I.O. ORDER WITH NO SPECIAL INSTRUCTION CODE, BUT ORDER ON AN ADVISE CODE (2). TECHNICAL PROCEDURE 1980 "X" SERIES BRAKE SERVICE INFORMATION IS FURNISHED WITH THIS BULLETIN AND IS TO BE USED WHEN REPLACING PARTS AS INSTRUCTED BELOW. ADDITIONAL BRAKE SERVICE INFORMATION IF REQUIRED IS LISTED IN GROUP 5 OF THE 1980 "X" SERIES SERVICE MANUAL. PART I - SERVICE PROCEDURE - A. REPLACEMENT OF REAR BRAKE SHOES AND LININGS 1. HOIST AND SUPPORT VEHICLE. 2. PRIOR TO INSTALLATION OF REAR BRAKE SHOES AND LININGS, INSPECT PARKING BRAKE CABLES FOR KINKS, DAMAGE, PROPER ROUTING AND THAT THEY APPLY AND RELEASE FREELY IN THEIR HOUSINGS. IF PARKING BRAKE SYSTEM DOES NOT OPERATE PROPERLY, CAUSE IS TO BE DETERMINED AND CORRECTED AS PART OF THIS CAMPAIGN. IF A VEHICLE IS EQUIPPED WITH MANUAL TRANSMISSION AND IS INVOLVED WITH THIS CAMPAIGN, REPLACE THE FRONT AND BOTH REAR PARKING BRAKE CABLES WHILE REPLACING REAR BRAKE SHOES AND LININGS (REFER TO PAGE 3 FOR CABLE PART NUMBERS). 3. REPLACE BOTH REAR BRAKE SHOE LINING ASSEMBLIES USING PARTS FROM LINING SET, P/N 12300194. REFER TO PAGE 9 OF THIS BULLETIN. A. THOROUGHLY CLEAN AND INSPECT BRAKE DRUMS FOR CRACKS, SCORES OR GROOVES. SMOOTH UP ANY SLIGHT SCORES. DRUMS WITH HEAVY SCORING SHOULD BE RESURFACED. REAR BRAKE DRUM SPECIFICATIONS INSIDE BRAKE DRUM SPECIFICATIONS INSIDE DIAMETER 7.879" (200.12 MM) RUNOUT .006" (.152 MM) REBORE DIAMETER 7.899" (200.64 MM) DISCARD DIAMETER 7.929" (201.40 MM)* *IF A BRAKE DRUM REQUIRES REPLACEMENT AND VEHICLE IS EQUIPPED WITH NON-FINNED DRUMS, REPLACE BOTH DRUMS WITH FINNED DRUMS, P/N 25516198. B. ADJUST BRAKE LINING TO DRUM. WHEN PROPERLY ADJUSTED THERE SHOULD BE NO BRAKE LINING DRAG WHEN DRUMS ARE ROTATED BY HAND. 1.) MEASURE THE INSIDE DIAMETER OF BRAKE DRUM WITH DRUM TO BRAKE SHOE CLEARANCE GAGE J-21177-A OR EQUIVALENT AS SHOWN IN VIEW A. 2.) POSITION TOOL ON BRAKE LININGS AS SHOWN IN VIEW B WITH SETTING OBTAINED IN STEP 1 AND ADJUST BRAKE SHOES SO THAT LINING CONTACTS OUTSIDE PORTION OF TOOL. B. ADJUST AND LUBRICATE PARKING BRAKE. 1.) USING GM WHEEL BEARING LUBRICANT P/N 1051344 (1 LB. CAN) OR EQUIVALENT, LUBRICATE ALL CABLE CONTACT POINTS, REAR EQUALIZER LEVER PIVOT AND EQUALIZER. 2.) DEPRESS PARKING BRAKE PEDAL EXACTLY THREE (3) RATCHET CLICKS. 3.) TIGHTEN ADJUSTING NUT UNTIL THE LEFT REAR WHEEL CAN BE TURNED REARWARD USING TWO HANDS BUT IS LOCKED WHEN FORWARD ROTATION IS ATTEMPTED. 4.) WITH MECHANISM TOTALLY DISENGAGED, REAR WHEELS SHOULD TURN FREELY IN EITHER DIRECTION WITH NO BRAKE DRAG. 5.) APPLY PARKING BRAKE 9 TO 16 RATCHET CLICKS 4 TO 5 TIMES TO INSURE IT IS COMPLETELY RELEASING AND OPERATING PROPERLY. NOTICE: IT IS VERY IMPORTANT THAT PARKING BRAKE IS NOT ADJUSTED TOO TIGHTLY CAUSING BRAKE DRAG. PART II - INSPECTION PROCEDURE - INSPECTION OF FRONT SHOE AND LININGS. THE FOLLOWING PROCEDURE IS NOT PART OF THE CAMPAIGN ACTION TO CORRECT THE CONDITION OF POSSIBLE PREMATURE REAR WHEEL SKID; ITS PURPOSE IS TO PROVIDE UNIFORMITY OF THE BRAKE SYSTEM. 1. REMOVE BOTH FRONT DISC BRAKE CALIPER ASSEMBLIES AND SUPPORT CALIPERS. REFER TO PAGE 10 OF THIS BULLETIN. DO NOT REMOVE OUTBOARD SHOES AND LININGS FROM CALIPERS FOR INSPECTION. A. INSPECT BOTH FRONT INBOARD AND OUTBOARD LININGS. IF REQUIRED, REPLACE SHOE AND LININGS WITH PARTS FROM THE PROPER SERVICE KIT. REFER TO PARTS INFORMATION SECTION OF THIS BULLETIN. REPLACE BOTH FRONT WHEEL SHOE AND LINING ASSEMBLIES IF THE GENERAL MOTORS LINING IDENTIFICATION IS NOT EVIDENT AS SHOWN IN ILLUSTRATION ON PAGE 7, OR AND ONE OF THE FOLLOWING CONDITIONS EXISTS. REFER TO PAGE 11 OF THIS BULLETIN FOR LINING REPLACEMENT. - ANY LINING WORN TO WITHIN 1/8" (3 MM) OF RIVET AT EITHER END OF SHOE. - ANY LINING NOT SECURELY ATTACHED TO SHOE. - ANY LINING SURFACE CONTAMINATED WITH GREASE, OIL OR IMBEDDED WITH FOREIGN MATERIAL. - ANY LINING SURFACE DAMAGED (CRACKED OR BROKEN). NOTICE: IF THE INSPECTION DETERMINED THAT THE FRONT SHOE AND LININGS DO NOT REQUIRE REPLACEMENT, INSPECT THE CALIPER ATTACHING BOLTS. IF ANY RUST OR CORROSION IS PRESENT ON BOLTS, REPLACE BOLTS, BUSHINGS AND SLEEVES. IT IS IMPORTANT THAT ALL THE NEW CALIPER ATTACHING PARTS FURNISHED IN THE FRONT BRAKE KIT BE USED WHEN SHOE AND LINING ARE REPLACED. ALL CALIPER MOUNTING EARS MUST BE PACKED WITH SILICONE GREASE AND NEW OUTBOARD SHOES CLINCHED AS SHOWN IN ON PAGES 10 AND 11 OF THIS BULLETIN. THE CALIPER BOLTS IN KIT REQUIRE A #50 TORX DRIVE FOR INSTALLATION. B. INSPECT ROTOR LINING SURFACES. LIGHT SCORING OF THE SURFACES NOT EXCEEDING .015" (.38 MM) IN DEPTH IS NOT DETRIMENTAL TO BRAKE OPERATION. IF SURFACE HAS DEEP SCORES OR IS DAMAGED SURFACE REFACE WILL BE REQUIRED AS LONG AS MINIMUM WEAR DIMENSION OF ROTOR IS MAINTAINED. FRONT BRAKE ROTOR SPECIFICATIONS DIAMETER 9.724" (247 MM) THICKNESS (MAXIMUM) .885" (22.48 MM) THICKNESS (MINIMUM REFINISH) .830" (21.08 MM) THICKNESS (REPLACE) .815" (20.70 MM) SURFACE FINISH 0.3-1.3 MICRO-METERS PARALLELISM (THICKNESS VARIATION) .0005" (.013 MM) MAXIMUM ALLOWABLE LATERAL RUNOUT .003" (.08 MM TIR) 2. REINSTALL CALIPER ASSEMBLIES. (REFER TO PAGE 10 OF THIS BULLETIN.) 3. REMOVE SUPPORT AND LOWER VEHICLE.

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.