HARSH ENGAGE, DOUBLE BUMP OR SHUDDER-PARK/NEUTRAL-REVERSE

THIS BULLETIN SUPERSEDES 87-7440-116 DATED 09/28/87, WHICH SHOULD NOW BE DISCARDED.

A new reverse band assembly that will help decrease harsh engagement, double "bump" or shudder from park or neutral to reverse in a vehicle equipped with a HYDRA-MATIC 4T60 (THM 440-T4) or THM F-7 transaxle. The new reverse band assembly has new friction material that will help decrease reverse engagement concerns.

Reverse engagement concerns can be caused by "oxidized" fluid (the fluid may visually appear to be OK), "glazed" (overheated) reverse band assembly friction material and/or improper surface finish on the drum of the 2nd clutch housing.

IMPORTANT: Harsh reverse engagement could also be caused by a worn or damaged rubber torsional damper unit (on models so equipped) that is incorporated as part of the right hand drive axle shaft. Refer to section 4D of the Service Manual.

SERVICE PROCEDURE:

Check engine idle speed, engine/transaxle mounts, rubber torsional damper unit for the right hand drive axle shaft (on models on equipped) and transaxle reverse line pressure following Service Manual procedures. If okay, replace the reverse band assembly and 2nd clutch housing drum and bushing assembly with the appropriate parts listed below in "Service Parts Information".

DATE OF PRODUCTION CHANGE:

Starting February 7, 1990 (Julian Date 038) all HYDRA-MATIC 4T60 (THM 440-T4) and THM F-7 transaxles will be built with the new reverse band assembly.

SERVICE PARTS INFORMATION:

Model Part Year Number Description

1984-90 8675152 Reverse Band Assembly

1987-90 8661912 2nd Clutch Housing Drum and Bushing Assembly (six plate)

1984-86 8668958 2nd Clutch Housing Drum and Bushing (five plate)

SERVICE MANUAL REFERENCE:

Refer to the HYDRA-MATIC 4T60 (THM 44--T4) Automatic Transaxle Unit Repair and On-Vehicle sections in the appropriate model year service manual for repair procedures.

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.