CAMPAIGN: TORQUE REAR BACKING PLATE CORROSION

JULY 1992 CAMPAIGN 2D11

1984-1985 S/T TRUCKS

DIRECT TORQUE REAR BACKING PLATE CORROSION (QUEBEC, ONTARIO & ATLANTIC PROVINCES)

MODELS: 1984-1985 S/T TRUCKS NOT PREVIOUSLY RECALLED IN THE PROVINCES OF QUEBEC AND ONTARIO AND 1985 S/T TRUCKS OM THE ATLANTIC PROVINCES

TO: ALL GENERAL MOTORS DEALERS

TRANSPORT CANADA HAS ADVISED GENERAL MOTORS OF CANADA LIMITED THAT THEY BELIEVE A SAFETY RELATED DEFECT MAY EXIST ON SOME 1984- 1985 S/T TRUCKS OPERATED IN CERTAIN PROVINCES BECAUSE THESE VEHICLES MAY DEVELOP A REAR BACKING PLATE CORROSION CONDITION, WHICH MAY RESULT IN WHEEL CYLINDER ROTATION OR MISPOSITIONING TO THE EXTENT THAT A PISTON NO LONGER CONTACTS A SHOE. THIS CONDITION RESULTED FROM INSUFFICIENT CORROSION PROTECTION TO WITHSTAND THE EXTREMELY SEVERE CORROSIVE ENVIRONMENT IN THE AFFECTED PROVINCES. WHEN THIS CONDITION OCCURS, A LOSS OF HYDRAULIC INTEGRITY MAY OCCUR RENDERING THE REAR BRAKES INOPERATIVE. THE FRONT BRAKES, WHICH SUPPLY APPROXIMATELY 70% OF THE BRAKING, REMAIN OPERATIONAL. HOWEVER, INCREASED STOPPING DISTANCES WILL BE REQUIRED.

TO PREVENT THIS CONDITION FROM OCCURRING, IT WILL BE NECESSARY TO INSTALL AN EXTERNAL WHEEL CYLINDER RETAINER ON EACH SIDE OF THE VEHICLE.

IN ADDITION TO THE CAMPAIGN SERVICE EXPLAINED ABOVE, DEALERS ARE ALSO TO INSPECT THE REAR BRAKE BACKING PLATES FOR RUST-THROUGH DUE TO CORROSION WHILE PERFORMING THE SERVICE PROCEDURE.

IF A BACKING PLATE IS FOUND WITH A RUST-THROUGH CONDITION, A NEW BACKING PLATE AND WHEEL CYLINDER ARE TO BE INSTALLED AT NO CHARGE TO THE OWNER. THE WHEEL CYLINDER RETAINER BRACKET IN THE PARTS KIT IS TO BE USED ON THE NEW WHEEL CYLINDER. THIS ADDITIONAL ACTION IS BEING TAKEN TO ASSURE CUSTOMER SATISFACTION WITH OUT PRODUCTS.

NORMAL MAINTENANCE ITEMS SUCH AS WORN BRAKE LININGS, LEAKING WHEEL CYLINDERS, PARKING BRAKE CABLES AND AXLE SEALS* FOUND DURING THE CAMPAIGN THAT REQUIRE REPLACEMENT WILL BE AT THE CUSTOMER'S EXPENSE. CUSTOMER MUST BE CONTACTED AND THEIR CONSENT OBTAINED PRIOR TO REPLACEMENT OF PARTS NOT COVERED BY THE CAMPAIGN.

* AXLE SEALS WILL BE COVERED WHEN BACKING PLATE REPLACEMENT IS REQUIRED.

VEHICLES INVOLVED:

INVOLVED ARE SOME 1984-1985 S/T TRUCKS IN THE PROVINCES OF QUEBEC AND ONTARIO AS WELL AS SOME 1985 S/T TRUCKS IN THE ATLANTIC PROVINCES BUILT WITHIN THE FOLLOWING VIN BREAK POINTS:

YEAR MODEL PLANT FROM TO

PROVINCES OF ONTARIO & QUEBEC

1984/1985 GMC S/T 0 SOP EOP 1984/1985 GMC S/T 2 SOP EOP

1984/1985 CHEVROLET S/T 0 SOP EOP 1984/1985 CHEVROLET S/T 2 SOP EOP

ATLANTIC PROVINCES

1985 GMC S/T 0 F0512864 EOP 1985 GMC S/T 2 F2513131 EOP

1985 CHEVROLET S/T 0 F0144953 EOP 1985 CHEVROLET S/T 2 F2149447 EOP

ALL AFFECTED VEHICLES HAVE BEEN IDENTIFIED BY THE VIN LISTING PROVIDED TO INVOLVED DEALERS WITH THIS BULLETIN. ANY DEALER NOT RECEIVING A LISTING WAS NOT SHIPPED ANY OF THE AFFECTED VEHICLES.

DEALER CAMPAIGN RESPONSIBILITY:

ALL UNSOLD NEW VEHICLES IN DEALER'S POSSESSION AND SUBJECT TO THIS CAMPAIGN MUST BE HELD AND INSPECTED/REPAIRED PER THE SERVICE PROCEDURE OF THIS CAMPAIGN BULLETIN BEFORE OWNERS TAKE POSSESSION OF THESE VEHICLES.

DEALERS ARE TO PERFORM THIS CAMPAIGN ON ALL INVOLVED VEHICLES AT NO CHARGE TO OWNERS, REGARDLESS OF KILOMETRES TRAVELED, AGE OF VEHICLE, OR OWNERSHIP, FROM THIS TIME FORWARD.

WHENEVER A VEHICLE SUBJECT TO THIS CAMPAIGN IS TAKEN INTO YOUR NEW OR USED VEHICLE INVENTORY, OR IT IS IN YOUR DEALERSHIP FOR SERVICE, YOU ARE TO ENSURE THE CAMPAIGN CORRECTION HAS BEEN MADE BEFORE SELLING OR RELEASING THE VEHICLE.

OWNERS OF VEHICLES RECENTLY SOLD FROM YOUR NEW VEHICLE INVENTORY ARE TO BE CONTACTED BY THE DEALER, AND ARRANGEMENTS MADE TO MAKE THE REQUIRED CORRECTION ACCORDING TO INSTRUCTIONS CONTAINED IN THIS BULLETIN.

IN SUMMARY, WHENEVER A VEHICLE SUBJECT TO THIS CAMPAIGN IS TAKEN INTO YOUR NEW OR USED VEHICLE INVENTORY, OR IS IN YOUR DEALERSHIP FOR SERVICE IN THE FUTURE, PLEASE TAKE THE STEPS NECESSARY TO BE SURE THE CAMPAIGN CORRECTION HAS BEEN MADE BEFORE SELLING OR RELEASING THE VEHICLE.

CAMPAIGN PROCEDURE:

REFER TO SECTION 4 OF THE SERVICE POLICIES AND PROCEDURES MANUAL FOR THE DETAILED PROCEDURE ON HANDLING PRODUCT CAMPAIGNS. DEALERS ARE REQUESTED TO COMPLETE THE CAMPAIGN ON ALL TRANSFERS AS SOON AS POSSIBLE.

OWNER NOTIFICATION:

ALL OWNERS OF RECORD AT THE TIME OF CAMPAIGN RELEASE ARE SHOWN ON THE ATTACHED COMPUTER LISTING AND HAVE BEEN NOTIFIED BY FIRST CLASS MAIL FROM GENERAL MOTORS. THE LISTINGS PROVIDED ARE FOR CAMPAIGN ACTIVITY ONLY AND SHOULD NOT BE USED FOR ANY OTHER PURPOSE.

PARTS INFORMATION:

PARTS REQUIRED TO COMPLETE THIS CAMPAIGN SHOULD BE ORDERED THROUGH REGULAR CHANNELS, AS FOLLOWS:

PART NUMBER DESCRIPTION QUANTITY/VEHICLE

18013604 WHEEL CYLINDER RETAINING BRACKET KIT 1 PER VEHICLE

18013524 BACKING PLATE (LEFT HAND) AS REQUIRED

18013525 BACKING PLATE (RIGHT HAND) AS REQUIRED

18012303 WHEEL CYLINDER (POWER BRAKES) AS REQUIRED

18012305 WHEEL CYLINDER (MANUAL BRAKES) AS REQUIRED

PARTS AND LABOUR CLAIM INFORMATION:

CREDIT FOR THE CAMPAIGN WORK PERFORMED WILL BE PAID UPON RECEIPT OF A PROPERLY COMPLETED CAMPAIGN CLAIM CARD OR DCS TRANSMISSION IN ACCORDANCE WITH THE FOLLOWING:

REPAIR CODE DESCRIPTION TIME ALLOWANCE

2A INSTALL BRACKET RETAINER KIT .5

3A INSTALL BRAKE RETAINER KIT AND REMOVE ONE .8 BRAKE DRUM TO PROPERLY REPOSITION THE WHEEL CYLINDER

4A INSTALL BRAKE RETAINER KIT AND REMOVE TWO 1.0 BRAKE DRUMS TO PROPERLY REPOSITION THE WHEEL CYLINDER

AA INSPECT BRAKES, REPLACE ONE BACKING PLATE 1.6 AND WHEEL CYLINDER AND INSTALL WHEEL CYLINDER RETAINING BRACKET KIT

BA INSPECT BRAKES, REPLACE TWO BACKING PLATES 2.2 AND WHEEL CYLINDERS AND INSTALL WHEEL CYLINDER RETAINING BRACKET KIT

REPLACEMENT OF AXLE SEAL(S) WHEN BACKING PLATE(S) REPLACEMENT IS REQUIRED, BOLTS, LUBRICATION OR REPLACEMENT OF AUTOMATIC BRAKE ADJUSTER MECHANISM - - THE AMOUNTS SHOULD BE ENTERED AS AN ADD CREDIT (7A).

TIME ALLOWANCE INCLUDES 0.1 HOUR FOR DEALER ADMINISTRATIVE DETAIL ASSOCIATED WITH THIS CAMPAIGN. PARTS CREDIT WILL BE BASED ON DEALER NET PLUS 30% TO COVER PARTS HANDLING. REPAIR CODES AA AND BA INCLUDE $3.50 FOR BRAKE FLUID.

SERVICE PROCEDURE:

USING PARTS FROM PART KIT NUMBER 18013604, INSTALL A WHEEL CYLINDER RETAINING BRACKET ON BOTH REAR WHEEL CYLINDERS USING THE FOLLOWING PROCEDURE:

1. HOIST AND SUPPORT VEHICLE.

2. USE A BRUSH AND SCRAPER TO REMOVE RUST AND DIRT BUILDUP FR AREAS 1, 2, AND 3 SHOWN IN FIGURE 1.

3. INSPECT THE FOLLOWING COMPONENTS:

A. BACKING PLATE FOR RUST-THROUGH CORROSION. HOLD TROUBLE LIGHT BEHIND BACKING PLATE (INBOARD SIDE) TO IDENTIFY CORROSION PERFORATION. REPLACE AS NECESSARY WITH NEW BACKING PLATE AND WHEEL CYLINDER. IF BACKING PLATE REPLACEMENT IS NECESSARY, SEE SERVICE MANUAL FOR PROCEDURE. (REPLACE AXLE SEALS FOR EACH AXLE SHAFT REMOVED).

B. AUTOMATIC BRAKE ADJUSTER MECHANISM FOR FREE MOVEMENT. LUBRICATE OR REPLACE AS NECESSARY.

*C. BRAKE SHOE AND LININGS FOR WEAR AND/OR CONTAMINATION.

*D. BRAKE DRUMS FOR WEAR AND /OR SCORING.

* THESE ITEMS ARE NOT COVERED BY THE CAMPAIGN. IF INSPECTION INDICATES THE NEED FOR SERVICE REPLACEMENT OR CORRECTION, APPROPRIATE RECOMMENDATIONS SHOULD BE MADE TO CUSTOMER.

4. PLACE A WHEEL CYLINDER BRACKET OVER BRAKE PIPE WITH BRACKET FINGER TOWARD THE WHEEL CYLINDER (FIGURE 2).

THE RETAINER BRACKET MUST FIT FLUSH AGAINST THE BACKING PLATE MOUNTING FLANGE WITH ALL FOUR (4) BRACKET FINGERS EXTENDING INTO THE HOLE TO GRASP THE WHEEL CYLINDER.

IN SOME CASES, IT MAY BE NECESSARY TO REPOSITION THE WHEEL CYLINDER TO PROPERLY INSTALL THE BRACKET. IF YOU CANNOT PROPERLY REPOSITION THE WHEEL CYLINDER, BRAKE DRUM REMOVAL MAY BE NECESSARY.

5. INSERT THE BOLT FROM THE KIT (P/N 18013604) THROUGH THE HOLE THE BRACKET AND START INTO THE CLIPPED ON NUT. USING A #8 EXTERNAL TORXN HEAD SOCKET, TIGHTEN THE BOLT TO 6.72 N.M (60|LBS. IN.).

THE BRACKET MAY TEND TO "WALK" INWARD DOWN THE AXLE TUBE AS THE BOLT IS TIGHTENED.

WHEN THE BRACKET IS PROPERLY INSTALLED, THE GAP BETWEEN THE BRACKET AND MOUNTING FLANGE MUST NOT EXCEED 3MM (7/64 IN.) (FIGURE|3). IF FINGERS DO NOT GRASP THE WHEEL CYLINDER AS SHOWN IN FIGURE 4 OR THE GAP IS GREATER THAN 3MM (7/64 IN.), REMOVE THE BRACKET AND REPEAT STEPS 2, 4, AND 5.

6. GRASP THE RETAINING BRACKET BY HAND AND TWIST. THE BRACKET SHOULD NOT MOVE. IF THE BRACKET CAN BE MOVED, IT SHOULD BE REINSTALLED, REPEATING STEPS 2, 4, AND 5.

7. REPEAT STEPS 2, 3, 4, 5, AND 6 TO INSTALL A BRACKET ON THE SIDE OF THE VEHICLE.

NOTE: WHEEL CYLINDER RETAINING KIT BRACKET IS TO BE INSTALLED ON ALL VEHICLES REGARDLESS OF WHETHER OR NOT BACKING PLATE REPLACEMENT WAS NECESSARY.

8. ADJUST REAR BRAKES FOLLOWING SERVICE MANUAL PROCEDURES. IF BACKING PLATE REPLACEMENT WAS NECESSARY, BLEED REAR BRAKE SYSTEM ACCORDING TO SERVICE MANUAL PROCEDURES.

9. TIGHTEN REAR WHEEL LUG NUTS TO TORQUE SPECIFIED IN SERVICE MANUAL.

10. INSTALL "CAMPAIGN IDENTIFICATION LABEL."

INSTALLATION OF CAMPAIGN IDENTIFICATION LABEL

CLEAN SURFACE OF RADIATOR UPPER MOUNTING PANEL AND APPLY A CAMPAIGN IDENTIFICATION LABEL. MAKE SURE THE CORRECT CAMPAIGN NUMBER IS INSERTED ON THE LABEL. THIS WILL INDICATE THAT THE CAMPAIGN HAS BEEN COMPLETED.

INSERT CAMPAIGN NUMBER

INSERT DEALER CODE

GENERAL MOTORS OF CANADA BULLETINS ARE INTENDED FOR USE BY PROFESSIONAL TECHNICIANS, NOT A "DO-IT-YOURSELFER." THEY ARE WRITTEN TO INFORM THESE 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 YOUR GENERAL MOTORS DEALER FOR INFORMATION ON WHETHER YOUR VEHICLE MAY BENEFIT FROM THE INFORMATION.

CUSTOMER SUPPORT DEPARTMENT GENERAL MOTORS OF CANADA LIMITED