EARLY BRAKE PAD WEAR AND/OR TIRE WEAR. GMC Truck GMC Suburban

SUBJECT: EARLY BRAKE PAD WEAR AND/OR TIRE WEAR (NEW STEERING AND BRAKE SYSTEM COMPONENTS)

MODELS: 1991-94 C3500HD MODELS BUILT PRIOR TO THE FOLLOWING VIN BREAKPOINTS:

1GBKC34F9RJ107933 CHEVROLET 1GDKC34FXRJ514540 GMC TRUCK

CONDITION:

SOME OWNERS MAY EXPERIENCE AN EARLY FRONT TIRE WEAR-OUT CONDITION IN THE RANGE OF 6,000-12,000 MILES. VEHICLES WHICH OPERATE PRIMARILY IN CITY SERVICE OPERATIONS, WHERE A HIGH NUMBER OF STEERING MANEUVERS ARE REQUIRED, WILL BE MORE LIKELY TO EXPERIENCE THIS CONDITION. IN ADDITION, SOME OWNERS MAY EXPERIENCE AN EARLY BRAKE PAD WEAR-OUT CONDITION. VEHICLES CARRYING HIGH CENTER OF GRAVITY LOADS IN STOP-AND-GO OPERATIONS ARE MOST SUSCEPTIBLE TO THE EARLY BRAKE PAD WEAR-OUT CONDITION.

CORRECTION:

AN INTERIM 1994 MODEL YEAR CHANGE WAS MADE IN PRODUCTION IN ORDER TO IMPROVE THE TIRE WEAR AND BRAKE WEAR CHARACTERISTICS OF THE C3500HD. THE CHANGES TO THE FRONT OF THE VEHICLE INCLUDE THE FOLLOWING: A REDESIGNED HUB AND ROTOR, A REDESIGNED STEERING ARM, LARGER VOLUME BRAKE PADS, A REDESIGNED ANCHOR PLATE AND SPLASH SHIELD, AND A REDESIGNED STEERING LINKAGE. CHANGES TO THE REAR OF THE VEHICLE INCLUDE THE FOLLOWING: A REDESIGNED ROTOR, LARGER VOLUME BRAKE PADS, AND A REDESIGNED ANCHOR PLATE. OTHER MISCELLANEOUS HARDWARE CHANGES WERE ALSO MADE AND ARE REFLECTED IN THE FOLLOWING INSTRUCTIONS.

THE FOLLOWING PROCEDURE DESCRIBES HOW TO RETROFIT A C3500HD MODEL WITH THE CHANGES MADE IN PRODUCTION. IT SHOULD BE NOTED THAT BECAUSE OF SOME SPECIFIC HARDWARE CHANGES, THE EARLY TIRE WEAR CONDITION CANNOT BE CORRECTED INDEPENDENTLY OF THE EARLY BRAKE PAD WEAR CONDITION. THEREFORE CORRECTING THE TIRE WEAR CONDITION NECESSITATES UPDATING THE FRONT BRAKE SYSTEM WHICH NECESSITATES UPDATING THE REAR BRAKE SYSTEM.

********************************************************************** THE FOLLOWING 'NOTE' WILL APPEAR IN CANADA'S BULLETIN ONLY. IT WILL BE REMOVED FROM THE PRINTED COPY IN THE U.S.A. **********************************************************************

**NOTE: IN CANADA, IMPLEMENTATION OF THIS BULLETIN REQUIRES PRIOR DISTRICT SERVICE MANAGER INSPECTION APPROVAL.**

FRONT END SERVICE PROCEDURE:

1. RAISE THE VEHICLE AND SUPPORT WITH SUITABLE SAFETY STANDS.

2. REMOVE THE WHEEL HUB/ROTOR ASSEMBLY FOLLOWING SECTION 3C OF THE SERVICE MANUAL.

3. DISCONNECT THE TIE ROD FROM THE STEERING ARM.

4. REMOVE THE ANCHOR PLATE, THE STEERING ARM AND THE SPLASH SHIELD FROM THE KNUCKLE.

5. CLEAN THE STEERING KNUCKLE MATING SURFACES.

6. REPEAT STEPS 1-5 ON THE OPPOSITE SIDE OF THE VEHICLE.

7. REMOVE THE TIE ROD ASSEMBLY FOLLOWING THE INSTRUCTIONS IN SECTION 3B3 OF THE SERVICE MANUAL.

8. ATTACH THE REDESIGNED SPLASH SHIELD TO THE REDESIGNED ANCHOR PLATE.

- USE THE 1/2 IN.(12.7 MM) LONG SPLASH SHIELD BOLTS AND SPLASH SHIELD WASHERS PROVIDED. (THE NEW BOLTS ARE SHORTER TO PROVIDE CLEARANCE TO THE HUB AND ROTOR).

- TORQUE THE BOLTS TO 16.5 N.M (12 LBS. FT.).

9. INSTALL THE REDESIGNED ANCHOR PLATE/SPLASH SHIELD ASSEMBLY AND THE REDESIGNED STEERING ARM ONTO THE STEERING KNUCKLE FOLLOWING THE INSTRUCTIONS GIVEN IN SECTION 3C OF THE SERVICE MANUAL.

- USE THE 2.75 IN. (70 MM) LONG, AND 4.25 IN. (108 MM) LONG BOLTS, WASHERS, AND NUTS PROVIDED. TORQUE THE NUTS TO 257 N.M (190 LBS. FT.).

- THE STEERING ARM STOP BOLT AND HEX JAM NUT PROVIDED IN THE KIT WILL NEED TO BE INSTALLED ON THE STEERING ARM. INSTALL AND ADJUST AS REQUIRED IN ORDER TO OBTAIN 35 DEGREES OF TURN ANGLE.

10. INSTALL THE REDESIGNED WHEEL HUB AND ROTOR ASSEMBLY FOLLOWING SECTION 3C OF THE SERVICE MANUAL.

- A NEW INNER BEARING SEAL IS PROVIDED IN THE SERVICE KIT.

- INSPECT THE WHEEL BEARINGS AS DESCRIBED IN SECTION 3C OF THE SERVICE MANUAL. REPLACE IF NECESSARY.

11. LUBRICATE THE BRAKE CALIPER AND ANCHOR PLATE GUIDEWAY SURFACES WITH AEROSHELL* #5 GREASE WHICH CAN BE OBTAINED AT A LOCAL SHELL* DISTRIBUTOR.

12. INSTALL THE REDESIGNED BRAKE PADS ONTO THE EXISTING CALIPER.

- DISCARD THE OLD BRAKE PADS.

- CRIMP THE OUTER BRAKE PAD FOLLOWING THE METHOD GIVEN IN SERVICE BULLETIN 465003 PUBLISHED IN JULY OF 1994.

- ENSURE THAT THE OUTER BRAKE PAD IS SECURE ON THE CALIPER. IF THE OUTER BRAKE PAD IS NOT SECURE ON THE CALIPER, A RATTLING NOISE MAY DEVELOP.

NOTICE: THE NEW BRAKE PADS WERE DESIGNED TO BE USED WITHOUT AN ANTI-RATTLE CLIP. DO NOT ATTEMPT TO USE THE OLD ANTI-RATTLE CLIP ON THE NEW BRAKE PADS OR BRAKE BIND-UP MAY OCCUR.

13. INSTALL THE BRAKE CALIPER ASSEMBLY FOLLOWING SECTION 5B1 OF THE SERVICE MANUAL.

- USE THE REDESIGNED CALIPER LOCK AND CALIPER SPRING PROVIDED.

NOTICE: THE OLD CALIPER LOCK AND CALIPER SPRING WILL NOT WORK ON THE NEW BRAKE SYSTEM.

14. INSTALL THE WHEEL AND TIRE ASSEMBLY. TORQUE NUTS TO 240 N.M (175 LBS. FT.).

15. REPEAT STEPS 8-14 ON THE OPPOSITE SIDE OF THE VEHICLE.

16. INSTALL THE REDESIGNED CRIMPED END OF THE TIE ROD ONTO THE TIE ROD ASSEMBLY.

17. INSTALL THE TIE ROD ASSEMBLY FOLLOWING THE PROCEDURE OUTLINED IN SECTION 3B3 OF THE SERVICE MANUAL.

18. ADJUST TOE-IN AS DESCRIBED IN SECTION 3A OF THE SERVICE MANUAL.

REAR END SERVICE PROCEDURE:

19. REMOVE THE HUB AND DRUM ASSEMBLY FROM THE VEHICLE FOLLOWING THE PROCEDURE GIVEN IN SECTION 4B1 OF THE SERVICE MANUAL.

20. REMOVE THE WHEEL BEARING OIL DEFLECTOR.

21. REMOVE THE ANCHOR PLATE AND DUST SHIELD FROM THE AXLE HOUSING MOUNTING FLANGE.

22. CLEAN THE AXLE HOUSING MOUNTING FLANGE MATING SURFACE.

23. INSTALL THE REDESIGNED ANCHOR PLATE AND REDESIGNED DUST SHIELD.

- ENSURE THAT THE ANCHOR PLATE MOUNTS FLUSH ON THE AXLE TUBE MOUNTING FLANGE. CHAMFER THE AXLE TUBE MOUNTING FLANGE IF NECESSARY (FIGURE 1).

- USE THE 1.9 IN. (48.26 MM) LONG BOLTS, WASHERS, AND NUTS PROVIDED. (THE NEW BOLTS ARE SHORTER TO PROVIDE CLEARANCE TO THE HUB AND ROTOR.)

- TORQUE THE NUTS TO 105 N.M (77 LBS. FT.).

24. INSTALL THE EXISTING WHEEL BEARING OIL DEFLECTOR.

25. CONNECT THE EXISTING WHEEL HUB TO THE REDESIGNED ROTOR USING THE WHEEL STUDS INCLUDED IN THE KIT.

26. INSPECT THE EXISTING WHEEL BEARINGS FOR WEAR, CHIPPED EDGES, OR OTHER DAMAGE. REPLACE THE BEARINGS IF NECESSARY.

27. INSTALL THE HUB AND ROTOR ASSEMBLY FOLLOWING THE PROCEDURE IN SECTION 4B1 OF THE SERVICE MANUAL.

28. LUBRICATE THE CALIPER AND ANCHOR PLATE GUIDEWAY SURFACES WITH AEROSHELL* #5 GREASE WHICH CAN BE OBTAINED AT A LOCAL SHELL* DISTRIBUTOR.

*WE BELIEVE THIS SOURCE AND THEIR PRODUCT TO BE RELIABLE. THERE MAY BE ADDITIONAL MANUFACTURERS OF SUCH A PRODUCT. GENERAL MOTORS DOES NOT ENDORSE, INDICATE ANY PREFERENCE FOR OR ASSUME ANY RESPONSIBILITY FOR THE PRODUCTS FROM THESE FIRMS OR FOR ANY SUCH ITEMS WHICH MAY BE AVAILABLE FROM OTHER SOURCES.

29. INSTALL THE REDESIGNED BRAKE PADS ONTO THE EXISTING CALIPER.

- DISCARD THE OLD BRAKE PADS.

- CRIMP THE OUTER BRAKE PAD FOLLOWING THE METHOD GIVEN IN SERVICE BULLETIN 465003 PUBLISHED IN JULY OF 1994.

- ENSURE THAT THE OUTER BRAKE PAD IS SECURE ON THE CALIPER. IF THE OUTER BRAKE PAD IS NOT SECURE ON THE CALIPER, A RATTLING NOISE MAY DEVELOP.

NOTICE: THE NEW BRAKE PADS WERE DESIGNED TO BE USED WITHOUT AN ANTI-RATTLE CLIP. DO NOT ATTEMPT TO USE THE OLD ANTI-RATTLE CLIP ON THE NEW BRAKE PADS OR BRAKE BIND-UP MAY OCCUR.

30. INSTALL THE CALIPER ASSEMBLY FOLLOWING SECTION 5B2 OF THE SERVICE MANUAL.

- USE THE REDESIGNED CALIPER LOCK AND CALIPER SPRING PROVIDED.

NOTICE: THE OLD CALIPER LOCK AND CALIPER SPRING WILL NOT WORK ON THE NEW BRAKE SYSTEM.

31. INSTALL THE TIRE/WHEEL ASSEMBLY.

- TORQUE THE WHEELS TO 240 N.M (175 LBS. FT.)

32. REPEAT STEPS 20-31 ON THE OPPOSITE SIDE OF THE VEHICLE.

SERVICE PARTS INFORMATION:

P/N DESCRIPTION QTY 12380416 STEERING AND BRAKE RETROFIT KIT 1

PARTS ARE CURRENTLY AVAILABLE FROM GMSPO.

WARRANTY INFORMATION:

FOR VEHICLES REPAIRED UNDER WARRANTY, USE:

LABOR OP DESCRIPTION LABOR TIME E8098 STEERING LINKAGE AND BRAKE SYSTEM RETROFIT 4.6 HRS.

NOTE: LABOR OPERATION IS CODED TO BASE VEHICLE COVERAGE IN THE WARRANTY SYSTEM.

FIGURES: 1

CAPTIONS: FIGURE 1 - REAR AXLE TUBE MOUNTING FLANGE

Object Number: 94498 Size: MF

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.