ENGINE NOISE-INSTALL BUSHING 5.7L V8 (RPO LT5)

SUBJECT: ENGINE NOISE (INSTALL NEW CRANKSHAFT BUSHING)

VEHICLES AFFECTED: 1990-92 CHEVROLET CORVETTE "ZR-1" WITH 5.7L ENGINE VIN J (RPO LT5) MANUAL TRANSMISSION ONLY

CONDITION:

---------- Some owners of 1990-92 Corvette ZR-1 may comment on a squeal noise that resembles a bearing noise. This noise may occur during clutch engagement from a standing stop. This noise can also occur during vehicle coast down with the clutch disengaged (clutch pedal depressed).

CAUSE:

------ This noise is due to the input shaft of the transmission contacting the crankshaft bushing. The noise usually occurs during clutch engagement from a standing stop or vehicle coast down because of the speed difference between the engine and the transmission input shaft.

CORRECTION:

----------- A revised crankshaft bushing is available to reduce the above condition. The revised bushing has grooves in the hole to reduce surface contact with the transmission input shaft.

Crankshaft Bushing P/N 10125896

Remove and install bushing per Service Manual.

For vehicles repaired under warranty use:

Labor Operation: J-1420 Labor Time: 3.6 Hrs. (Model Years 1990 and 1991 Only) 3.3 Hrs. (Model Year 1992 Only) 0.2 Hr. (Add on for Replacing Clutch Bearing/Bushing)

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.