NEW CLUTCH DESIGN IMPLEMENTED PRESSURE PLATE & FLY WHEEL

EFFECTIVE WITH THE 1987 MODEL YEAR (VIN J8DB4B1HOH8301533), A NEW CLUTCH DESIGN WAS IMPLEMENTED. THE NEW CLUTCH DIAMETER HAS BEEN INCREASED FROM 10.83 INCHES (275 MM) TO 11.8 INCHES (300 MM). IN CONJUNCTION, THE PRESSURE PLATE AND FLYWHEEL HAVE BEEN REDESIGNED TO ACCOMMODATE THE INCREASED DIAMETER.

SPECIAL NOTE:

THE 11.8 INCH CLUTCH DISC/PRESSURE PLATE AND COMPONENTS (INCLUDING THE FLYWHEEL AND HOUSING) ARE NOT INTERCHANGEABLE WITH EARLIER PRODUCTION CLUTCH ASSEMBLIES.

TO SERVICE THE 1986 W4 MODELS, A HEAVY DUTY CERAMETALLIC CLUTCH DISC, 10.8 INCHES (275 MM), HAS BEEN RELEASED FOR SERVICE USAGE ONLY. THIS SERVICE CLUTCH DISC HAS BEEN DESIGNED TO PROVIDE IMPROVED CLUTCH DURABILITY AND PERFORMANCE FOR A WIDE RANGE OF APPLICATIONS. THE CERAMETALLIC CLUTCH IS A DIRECT REPLACEMENT FOR THE EARLIER DESIGN, AND INSTALLATION MAY BE MADE WITHOUT CHANGING THE EXISTING PRESSURE PLATE.

INSTALLATION OF THIS HEAVY DUTY CLUTCH DISC CAN BENEFIT APPLICATIONS WHERE THE FOLLOWING KINDS OF CONDITIONS EXIST.

1) HIGH GVW APPLICATIONS 2) MULTIPLE/INEXPERIENCED OPERATORS 3) POOR ROAD CONDITIONS AND HEAVY TRAFFIC CONGESTION

IN ORDER TO MAXIMIZE CLUTCH DURABILITY AND PERFORMANCE, LISTED BELOW ARE ITEMS WHICH MUST BE CHECKED, ADJUSTED, REPAIRED OR REPLACED IF NECESSARY AT THE TIME OF SERVICING. FOR MORE DETAILED INSTRUCTION ON DISASSEMBLY, INSPECTION AND REASSEMBLY PROCEDURES, REFER TO THE APPROPRIATE GMC TRUCK SERVICE MANUAL.

1) PEDAL (MASTER CYLINDER) FREEPLAY AND PEDAL HEIGHT.

2) PRELOAD ON CLUTCH SLAVE CYLINDER

PRELOAD CAN BE DETERMINED BY MANUALLY PRESSING THE CLUTCH RELEASE LEVER IN THE DIRECTION OF THE SLAVE CYLINDER (SEE FIGURE 1). IF MOVEMENT IS NOT OBSERVED, REFER TO TRUCK SERVICE BULLETIN 87-T-82.

3) CHECK FOR LEAKAGE THROUGHOUT CLUTCH HYDRAULIC SYSTEM.

4) FLYWHEEL AND CLUTCH PRESSURE PLATE SURFACE CONDITION.

USE OF CERAMETALLIC CLUTCH DISC MAY RESULT IN A SLIGHT INCREASE IN SHIFT EFFORT AND A MORE AGGRESSIVE ENGAGEMENT. THIS IS A NORMAL CHARACTERISTIC OF THIS TYPE OF CLUTCH DISC AND IS NOT GENERALLY OBJECTIONABLE, ALTHOUGH YOUR CUSTOMER SHOULD BE ADVISED AT THE TIME YOU RECOMMEND INSTALLATION THAT THESE ARE THE CHARACTERISTICS OF A CERAMETALLIC CLUTCH DISC:

PARTS ARE AVAILABLE THROUGH GMSPO BY ORDERING THE FOLLOWING PART NUMBER:

94463570 - CERAMETALLIC CLUTCH DISC - 10.8 INCHES (275 MM)

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.