CLUTCH BEARING NOISE OR PEDAL VIBRATION

CLUTCH NOISE

VEHICLE AFFECTED 1985-87 S/T TRUCKS WITH MANUAL ---------------- TRANSMISSIONS

With the introduction of the hydraulic clutch system in 1985, the design uses a constant running throw-out bearing which rides against the diaphragm fingers on the pressure plate with approximately 53 N (12 lbs) of pressure. When the fingers become out of plane (different finger heights) the clutch fork will move fore and aft. After time, the ball stud in which the fork pivots becomes dry (from lack of lubrication) and begins to squeak.

To repair this condition, it will be necessary to replace the clutch plate and disc with the part numbers listed below. The new plate has fingers which have closer tolerances. Also, the ball stud and fork should be replaced, as fretting may have occurred between the stud and the fork. The fork and ball stud should be lubricated with front wheel bearing grease prior to installation.

PARTS

P/N 15608690 Disc 2.5L (LN8) P/N 15608691 Disc 2.8L (LL2) P/N 15608692 Clutch Plate

P/N 14036046 Ball Stud

P/N 14070374 Clutch Fork

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.