ERRATIC OR NO UPSHIFT NEW GOVERNOR DRIVEN GEAR

TRANSMISSION APPLICATIONS: SUBJECT: ------------------------- ------- 1978 THROUGH 1988 ERRATIC OR NO UPSHIFT - SERVICE AND THM 400/475 (M40/M41) PARTS INFORMATION FOR A NEW GOVERNOR 1982 THROUGH 1988 DRIVEN GEAR THM 700-R4 (MD8)

TRANSMISSION MODELS: VEHICLE APPLICATIONS: ------------------- -------------------- ALL MODELS THM 400/475 VEHICLE APPLICATIONS: C, K, R, V, P - Trucks; G - Van THM 700-R4 VEHICLE APPLICATIONS: B, F, Y - Cars; C, K, R, V, S, T - Trucks; G, M - Vans

BULLETIN COVERS:

A THM 400/475 or 700-R4 transmission with an erratic or no upshift condition which may be due to applecoring of the governor driven gear. "Applecoring" of the governor driven gear (refer to Figure 2) may be caused by nicks and/or burrs on the governor drive gear. The new governor driven gear has a higher fiberglass content. Also, inspect the output shaft for nicks and/or burrs on the governor drive gear. Replace the output shaft if nicks and/or burrs are found.

DATE OF PRODUCTION CHANGE: (Figure 1) ------------------------- Beginning December 11, 1987 (Julian Date 345) all THM 400/475 transmissions were produced with the new governor driven gear.

Beginning July 06, 1987 (Julian Date 187) all THM 700-R4 transmissions were produced with the new governor driven gear.

SERVICE ACTION:

When servicing any THM 400/475 governor driven gear, use the nww governor driven gear and pin package listed under "Service Parts information".

When servicing any THM 700-R4 governor driven gear for an "applecored" condition, use the new governor driven gear and pin package listed under "Service Parts Information". NOTE: The new THM 700-R4 governor gear is green in color (the previous gear was blue.) This can be used as another method of identification.

When servicing any 1982 through 1986 THM 700-R4 governor driven gear for conditions other than applecoring, the previous governor driven gear, package number 8642928, should be used until current service stock is depleted.

SERVICE PARTS INFORMATION:

Part No. Description ------- ----------- 8663995 THM 700-R4 - Governor Drive Gear and Pin Package 8629977 THM 400 - Governor Drive Gear and Pin Package

SERVICE MANUAL REFERENCE:

Refer to the appropriate 1988 Unit Repair Service Manual sections for removal and installation procedures not covered in this bulletin.

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.