C/C SURGE ABOVE 50 MPH CHECK VSS DRIVE/ DRIVEN GEAR

VEHICLES AFFECTED: 1985-87 DE VILLES AND FLEETWOODS

Some 1985-1987 De Villes and Fleetwoods may experience a condition of slight cruise control surge. This condition usually occurs above 50 mph (80 kmh) and is more pronounced after reaching normal operating temperatures. This condition may be caused by an erratic Vehicle Speed Sensor (VSS) input, which may not be detected by viewing the VSS parameter of vehicle diagnostics. This erratic input may be caused by looseness in the VSS drive and driven gear.

To repair this condition, proceed as follows:

1. Remove VSS and governor assembly.

2. Inspect VSS drive and driven gears for damaged or broken teeth and replace as necessary. If the condition persists, proceed to Step 3.

3. Obtain .005" (.127mm) brass shim stock.

4. Using the .005" brass shim stock, cut a piece 5/16" x 1-9/16" (8 x 40mm).

5. Remove governor gear (pull off).

6. Wrap this shim around the governor shaft and install drive gear over the shim ensuring a press fit and eliminating any looseness (see Figure 1).

7. Shim stock should not cover bearing contact surface, trim flush with the top of the gear if necessary.

8. Remove VSS gear (pull off).

9. Using the .005" brass shim stock, cut a piece 15/16" x 1/4" (1-4 x 24mm) and wrap this shim around the VSS shaft and install gear onto shaft, ensuring all looseness is eliminated. (See Figure 2).

10. Trim excess shim stock if necessary.

Use applicable Labour Operation and Time.

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.