Condition: Some 1989-91 Grand Prix models equipped with auxiliary rear springs may exhibit a thud/clunk type noise coming from the rear of the vehicle that is audible in the passenger compartment. This condition is most apparent after a harsh/sharp road input such as a chuck-hole/ speed bump.
Cause: Auxiliary rear spring lower attaching bracket not in,full contact with rear spindle rod. Under certain operating conditions lower attaching bracket may flex and contact spindle rod resulting in thud/clunk noise.
Correction: Following service procedure indicated below, insure that the auxiliary rear spring lower brackets are properly seated on spindle rods.
1. Raise vehicle and support in such a manner that rear suspension is extended in a full downward position.
2. Inspect both right and left hand auxiliary spring lower brackets to insure they are in contact with spindle rods utilizing a .002" feeler gage.
3. If a bracket is not in contact, loosen lower bracket to spindle rod bolt a maximum of two revolutions. Let bracket position itself on spindle rod and re-torque bolt(s) to 46 N.m (36 lbs. ft.).
THE AUXILIARY SPRINGS ARE UNDER COMPRESSION AND BOLTS MUST NOT BE REMOVED. DOING SO MAY RESULT IN PERSONAL INJURY.
4. Lower vehicle.
Labor Operation Number: T1752 Labor Time : 0.3 Hours
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.