FLUID LEAKS AT SPEEDO DRIVE GEAR AND ADAPTER AREA

MODEL AND YEAR: ALL 1986 AND 1987 LIGHT DUTY TRUCKS WITH MANUAL OR AUTOMATIC TRANSMISSIONS

BULLETIN COVERS:

Transmission fluld leak at the plastic speedometer driven gear (44, Figure No. 1) can be caused by a hole in the driven gear shaft. In some cases, this condition could be misdiagnosed as a speedo driven gear fitting leak (43, Figure No. 1).

SERVICE ACTION:

When servicing a 1986 or 1987 vehicle for a fluid leak around the speedometer driven gear fitting or cable, check the speedometer driven gear shaft for a hole through the center of the shaft as follows: (Figure No. 2)

1. Install a hand vacuum pump over the end of the gear (opposite gear teeth).

2. Pump up 10 in.-hg. of vacuum.

3. The gage should stay at 10 in.-hg. for at least 30 seconds.

-If the gear holds vacuum, inspect the seals in the adaptor.

-If the gear does not hold vacuum, replace the gear.*

*Note: Check the new gear from parts stock as outlined before installing in transmission.

SERVICE PARTS:

Refer to the GM Service Parts Operations (GMSPO) Catalog for the current speedometer gear based on transmission model and year.

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.