A/C NOISE/VIBRATION INSTALL BRACE KIT

Subject: AIR CONDITIONER NOISE/VIBRATION

Model and Year: 1988-91 C/K, R/V TRUCKS WITH 7.4 ENGINE

Condition: Some C/K and R/V trucks with 7.4L engine may exhibit a noise/vibration when the air conditioning is engaged.

Cause: This noise/vibration is the result of a resonance set up in the serpentine accessory drive system with air conditioning on.

Correction: This condition may be improved by installing a brace kit. The installation instruction included in the brace kit must be followed carefully. On some trucks, the addition of an inertia ring pulley may be required. On C/K models refer to Dealer Service Bulletin No. 90-382-1 D for new Suction Discharge Hose Assembly.

Model Year Part Number Description ---------- ----------- ------------------------------------ 1988-91 6553148 Pulley and Bearing Assembly A/C Comp. 1988-90 10187643 Brace Kit - A/C Vibration and Noise 1991 10187645 Brace Kit - A/C Vibration and Noise

Parts are currently available from GMSPO.

1988-90 Labor Operation Number: T7286 Labor Time: .9 Hours (plus .2 Hrs. for skid plate)

1991 Labor Operation Number: T7287 Labor Time: .4 Hours (plus .2 Hrs. for skid plate)

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.