Some 1985-1987 De Villes and Fleetwoods, and 1986-1987 Eldorados and Sevilles equipped with a THM440-T4 transaxle, may exhibit a harsh engagement or engagement shudder from park or neutral to reverse.
This condition may be caused by contaminated oil (oxidized) or may be the result of slip between the reverse band and the second clutch drum.
To repair this condition, check for correct engine idle speed and loose or worn engine/transaxle mounts and repair as necessary. If okay, drain and refill the transaxle fluid and test for the above condition. If the condition still exists, replace the reverse band and second clutch drum with the following service part numbers.
Year Part Number Description ---- ----------- ----------- 1985-1987 8658890 Reverse Band 1985-1986 Model (5-plates) 8646929 Second Clutch Drum Assembly 1987 Model (6-plates) 8661912 Second Clutch Drum Assembly
For warranty purposes, use Labor Operation K7535 at 6.0 hours for De Villes and Fleetwoods, and 6.6 hours for Eldorados and Sevilles.
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.