Transmission - Leak from Speedometer Gear/Adaptor
Number: 87-138Section: 7A
Date: May, 1987
Subject: FLUID LEAKS FROM THE PLASTIC SPEEDOMETER DRIVEN GEAR/ADAPTOR AREA
Model and Year: ALL 1986 AND 1987 LIGHT DUTY TRUCKS WITH MANUAL OR AUTOMATIC
TRANSMISSIONS
Figure No. 1EXTENSION AND ASSOCIATED PARTS:
BULLETIN COVERS:
Transmission fluid 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).
Figure No. 2:
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.