POPPING NOISE WHEN BRAKING FORE / AFT SHIFT OF FRAME

VEHICLES AFFECTED: All 1984-86 'A' Models and 1984-85 'X' Models

Some 1984-86 'A' and 1984-85 'X' cars may exhibit a popping type noise during braking and acceleration. The popping noise, caused by a fore and aft shifting of the cradle, can be felt as 'oil canning' in the floor pan. (The popping noise should not be confused with a 'click' or 'clunk' felt in the steering wheel -- covered in Product Service Bulletin 84-3-120). Another similar sounding noise, 'crunching' could be caused by loose cradle mount bolts. Torque should be 115 N.m (85 ft. lbs.)

Product Service Bulletin 85-3-131 has been revised to include 1986 'A' cars assembled prior to dates and VIN breakpoints noted below by assembly plant.

Oshawa Plant 1

2/14/86 Oldsmobile 2G3AM19X2G9335808 2/7/86 Pontiac 2G2AG19XOG9268024

Oshawa Plant 2

3/3/86 Chevrolet 2GlAW19XXG1215918

Oklahoma

1/20/86 Chevrolet lGlAW35RlG6177295 1/20/86 Buick lG4AL19R4G6442527

Framingham

2/10/86 Chevrolet lGlAW35X8GG123050 2/10/86 Oldsmobile lG3AJ19R6GG364241

Tarrytown

1/17/86 Pontiac lG2AF27XlGT228880 1/17/86 Buick lG4AH19X7GT459369

Doraville

2/28/86 Oldsmobile lG3AJ19ROGD406565 2/28/86 Buick lG4AL353OGD443229

If the noise is still present after tightening the cradle bolts, it can be corrected by installing shims on both rear cradle mount insulators as shown. The intent of this fix is to create an interference fit using shims. Multiple shims may be used if necessary.

Shims may be fabricated from any available steel or brass shim stock. Thickness should be approximately .64mm (.025 in.) to 1.02mm (.040 in.)

The following procedure should be followed when installing shims:

1. Support cradle with a jack stand on the rear cross member.

2. Remove one (1) rear cradle bolt at a time and lower the jack stand enough from the mount.

CAUTION:

Damage to the steering intermediate shaft could result if the cradle is lowered more than required to free the mount.

3. Form shim to mount as shown and reinstall mount. Some rubber lube may be required to ease assembly.

4. Reinstall mount bolt. Torque to 115 N.m (85 ft. lbs.)

5. Repeat above procedure on other rear corner.

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.