ERRATIC OR NO UPSHIFT NEW GOVERNOR DRIVEN GEAR

Model and Year: 1987-88 VEHICLES WITH THM 400/475 OR THM 700-R4 TRANSMISSIONS

A THM 400/475 or THM 700-R4 transmission with an erratic or no upshift condition may be created by "applecoring" of the governor driven gear. "Applecoring" is pictured in the illustration below.

A new governor driven gear with a higher fiberglass content entered production on all THM 400/475 transmissions December 11, 1987 (Julian date 345) . THM 700-R4 transmissions were produced with a new gear beginning July 6, 1987 (Julian date 187).

"Applecoring" of the governor driven gear may be the result of nicks or burrs present on the output shaft drive gear. Inspection of the output shaft should be performed and if nicks or burrs are present the output shaft should be replaced.

The new service part numbers are listed below for each model transmission.

Part No. Description

8663995 THM 700-R4 - Governor Driven Gear and Pin Package

8629977 THM 400 - Governor Driven Gear and Pin Package

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.