NOISE FROM REAR OF VEHICLE CAUSES AND CORRECTIONS

Some Celebritys and Citations may exhibit a thumping condition best described as a "loose lumber" noise in the rear of the car. This condition is most noticeable over certain road surfaces, such as those with raised expansion strips or pot holes.

This bulletin outlines three (3) corrections (A, B and C) for rear suspension noise. The correction for what is commonly called "loose lumber" noise is outlined in Section A.

(A) Subject vehicles exhibiting a "loose lumber" condition may be improved by replacing the rear shock absorbers with shocks that have tighter shock valving. This modified shock absorber is available in service kit, P/N 4993583, for Celebrity and Citation series less RPO Z19.

(B) To further reduce rear suspension complaints, the secondary spring (jounce bumper) may be shortened 10mm as described below:

1. Open the deck lid, remove trim cover and remove upper shock attaching nut, retainer and grommet, from both shock absorbers.

2. Raise the car on a hoist that supports the rear axle assembly.

3. Remove lower attaching bolt, nut and shock absorber on each side.

4. Remove the shield, by pulling downward and twisting, from both shocks (Figure 1).

5. Pull, while rotating, secondary spring down from the top of the shock not more than 6mm (1/4"). Using a hacksaw, cut 10mm (7/16") off of the top of the rubber secondary spring. Split the section of rubber that has been cut away, remove and discard. Do this to both shock absorbers. Take care not to damage the shock absorber rod below the secondary spring.

6. Push the secondary springs back to the top of the shock absorber shafts and reinstall the shields by twisting to re-engage with secondary spring tabs.

7. Re-install the shocks at their lower attachment brackets, feed the bolts through and loosely install the nuts. Guide the upper shock studs through the body openings and torque the lower shock attaching nuts to 58 N.m (43 ft. lbs.).

8. Lower the car and install the grommets, retainers and upper shock attaching nuts. Torque to 17 N.m (13 ft. lbs.), install trim cover and close the deck lid.

(C) One further noise correction in the rear suspension area would be to replace the stabilizer bar damper with damper, P/N 10025934. (The new damper keeps the stabilizer bar from going into resonance during road impacts and causing a "ringing type" noise.)

Labor Operation Numbers and Labor Time:

Item A above . . . . . . . . . . . . . . T1085 .5 hours

Item B above . . . . . . . . . . . . . . T1080 .6 hours

Item C above . . . . . . . . . . . . . . E4186 .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.