For 1990-2009 cars

# DRIVE AXLE 'WOBBLE' VIBRATION S-PLAN SPIDERS/BEARING BLOCKS

#### SUBJECT: DRIVE AXLE 'WOBBLE' VIBRATION BETWEEN 20-35 MPH - INSTALL S-PLAN SPIDERS AND BEARING BLOCKS

#### MODELS/YEARS 1988-92 TORONADO/TROFEO'

Some 1988-92 Toronado/Trofeo' models built before vehicle number NU306007 may exhibit an intermittent vibration with a light engine load between 20-35 mph. This 'wobble' condition is often described as a side-to-side motion of the front of the vehicle, similar to when a belt is damaged in a radial tire.

This condition is caused by an intermittent binding condition of the S-plan inboard drive axle joints. This binding condition only occurs while the joint is rotating at vehicle speed with an engine load. The S-plan joint will not cause a vibration on a closed throttle coast down.

This condition may be repaired by installing revised S-plan spiders and bearing blocks in both drive axles. Use the procedure below The spider service kit, P/N 26039083, includes one spider, three bearing blocks, and two retaining clips. Kits are currently available from GMSPO. Two kits are required per vehicle. The revised spider incorporates polished surfaces and the bearing blocks have been enlarged. These changes went into production at the breakpoint mentioned above.

1 . Verify that the condition is not caused by tire imbalance. Refer to Section 3 of the appropriate service manual for tire balance diagnosis and repair.

2. Install two service spider kits (one per axle), following the service procedures in Section 4D of the appropriate service manual.

3. During joint disassembly, it is NOT necessary to remove the grease from the joint housing. The grease can be reused during reassembly with the new spider and bearing blocks.

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.