TORQUE STEER ON ACCELERATION MAYBE ENGINE/TRANSAXLE ALIGN

SLIGHT TORQUE STEER ON ACCELERATION

MODELS AFFECTED: 1986-87 RIVIERAS ---------------- NOTICE: This bulletin is being revised to include Shim Part Number not included in 87-3-13. Discard bulletin 87-3-13 and replace with this bulletin.

A condition of slight torque steer to the left, during acceleration, may be experienced on some 1986-81 Rivieras. This condition may be caused by the engine/transaxle assembly being misaligned in the cradle, resulting in improper drive axle operating angles.

Torque steer should not be confused with radial tire pull or lead. Review the radial tire lead/pull and torque steer diagnosis in Section 3 of the Chassis Service Manual.

DEFINITIONS

Lead or Pull: Vehicle movement to the left or right, at a constant speed, from a straight path on a level road with hands off the steering wheel.

Torque Steer: Vehicle and steering wheel movement to the left or right (from driver's seat position) on acceleration.

PRELIMINARY INSPECTIONS

1. Inspect cradle and suspension components for damage or misalignment. 2. Inspect front brakes for binding calipers or sticking caliper pistons. 3. Verity that front end alignment, tire inflation, and trim height are within specifications.

NOTICE: Alignment equipment must be within calibration specifications. Do not exceed one (1) degree cross camber.

4. Inspect drive axles for damage and/or binding.

REPAIR PROCEDURE

1. Change the front tires from side to side and road test vehicle. If the condition is corrected or the vehicle now leads to the opposite direction, the tires should be considered as the cause and replaced if necessary. If no change is noted, proceed with Steps 2 thru 6.

2. Loosen the engine/transaxle to cradle mounts and allow the assembly to settle.

3. Disconnect the exhaust pipe from the exhaust manifold.

4. Remove the left hand transaxle mount with bracket. Replace the mount with Part Number 17989560, reusing the bracket. Parts are currently available from GMSPO.

NOTICE: Make sure the hood is raised to avoid damage during engine jacking.

5. Shift the right front engine mount to the extreme left side (driver's side) of the frame slots.

NOTICE: Do not attempt to retrofit 1986 engine mount with 1987 engine hydromount.

6. Retighten all engine/transaxle to cradle mount fasteners. Reconnect exhaust pipe.

At this point, the vehicle should be road tested again to determine if the torque steer condition has been repaired.

If road test indicates some torque steer still exists, shim the left hand transaxle mount (Refer to Figure 1) by 2 m increments up to a maximum of 8 mm using Part Number 1647076. Road test after each increment to determine need for additional shimming. Check to ensure the left hand transaxle mount interlock hook has a minimum clearance of 3m. There should be no metal to metal contact.

Parts are expected to be available on November 21, 1988. Until then, normal part orders will not be accepted by GMSPO. Only verifiable emergency VIP orders will be accepted. SPO will make every effort to obtain parts. All parts will be placed on 400 control to waive VIP surcharges. However, the part will be shipped premium transportation at dealer's expense. All other order types will be canceled as incorrectly ordered while the 400 control is in place.

WARRANTY INFORMATION

For repair procedure Steps 2 thru 6:

Labor Operation Number: T5156 Labor Time: 1.2 Hours Trouble Code: 92

For shimming left hand transaxle mount, add .3 for each 2mm increment.

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.