SLIPS IN REVERSE BURNED CLUTCH PLATES

If a 1984 Model THM 700-R4 transmission experiences a "slips in reverse" along with burned lo and reverse clutch plates, a possible cause may be an incorrectly machined boss bolt hole at the end of the line bias valve (Fig. 1). The boss surface may have been machined off about 0.040"-0.050" too much. This allows the valve body attaching bolt that locates through the sleeve at the end of the line bias valve to interfere with the lo and reverse clutch plates, preventing them from releasing properly. When this occurs, the bolt end and the clutch plates will have wear or burrs.

SERVICE PROCEDURE:

1. Remove lo & reverse clutch assembly from transmission.

2. Check clutch plates for evidence of burrs caused by bolt interference.

3. If still not sure, install valve body back on transmission and check inside case to determine if bolt protruding is through.

4. Remove the bolt that is located at the end of the line bias valve.

5. Install a 2mm (0.080") washer under bolt head (Fig. 1).

NOTICE: If the bolt already has a washer, be certain when reassembling the washer that it is in the correct location.

6. Reassemble, following procedure outlined in the service manual.

NOTICE: Washer is not required, if above condition does not exist. Adding washer, when not needed, could result in stripping bolt threads in case.

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.