REAR SUSPENSION NOISE DIAGNOSIS & PROCEDURE

Models Affected: 1987-89 BONNEVILLE MODELS

This bulletin cancels and replaces bulletin 89-3-17A issued 12/89. This bulletin has been revised to update parts information under 'straight rate spring'. Rear suspension noise on some 1987 through 1989 Bonneville models can be caused by the following:

Spring Contact With Body Flange

This condition can be verified by visual inspection for any signs of contact between the coil spring and the body flange. If this condition exists, the following should be done.

The body flange sheet metal should be carefully repositioned to maximize clearance. Apply paint and/or rustproofing material as needed to prevent corrosion.

Inspect the coil springs for proper position. If necessary, position the springs as shown in the illustration below, taken from the 1989 Service Manual, so that the ends of the spring pigtails are positioned outboard. Note that this orientation is different than that shown in the 1987 thru 1988 Chassis Service Manuals.

Top spring coils contact each other 1987 (cars without Electronic Level Control)

This condition can occur in the variable rate design springs used on 1987 Bonneville cars without Electronic Level Control. If this condition is suspected, it can be verified by installing insulating material (heater hose or equivalent) to the top coils and test driving. If the noise is eliminated with the insulating material, the rear coil springs should be replaced with the appropriate springs from GMSPO.

If the suspension noise is determined to be caused by the rear variable rate coil springs, and the noise cannot be eliminated by any of the above methods (including replacing the original variable rate rear coil springs with new variable rate rear coil springs), the variable rate springs may be replaced with straight rate springs (both sides must be replaced) according to the following table:

VARIABLE RATE SPRING STRAIGHT RATE SPRING --------------------- -------------------- Production Service Service Part Number Code Part Number Code Part Number ----------- ---- ----------- ---- ------------ 25530364 RRS 25530363 NZE 25524843 25530363 RRR 25530363 NZE 25524843 25530362 RRO 25530363 NZE 25524843 25530361 RRN 25530361 NZC 25524841 25530360 RRM 25530361 NZC 25524841 25530359 RRL 25530359 MBG 25526961 25530358 RRK 25530359 MBG 25526961

Parts are currently available from GMSPO.

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.