FLUID LEAKS AT SPEEDO DRIVEN GEAR/ADAPTER AREA

VEHICLE APPLICATIONS

THM 200C - E TRUCK; THM 400 - C, K, R, V, AND P TRUCKS THM 700-R4 - ,C, K, R, V, S AND T TRUCKS, G AND M VANS

BULLETIN COVERS:

Transmission fluid leak at the plastic speedometer driven gear (44, Figure 1) can be caused by a hole in the driven gear shaft. This condition could be misdiagnosed as a speedo driven gear fitting leak (43, Figure 1).

SERVICE ACTION:

When servicing a 1986 or 1987 THM 200C, 400 or 700-R4 transmission for a fluid leak around the seeedometer driven gear fitting or cable, check the speedometer driven gear shaft for a hole through the center of the shaft as follows: (Figure 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 gauge 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 Catalogue 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.