SLIP OR LOSS OF DRIVE AND/OR BURNT FORWARD & OVERUN CLUTCH

MODELS: 1987 LIGHT DUTY MODELS WITH THM 700-R4 AUTOMATIC TRANSMISSIONS

BULLETIN COVERS: (Figure No. 1) --------------- A new auxiliary accumulator valve body (377) and a new cover (371) went into production to prevent the accumulator piston pin from working its way out of the auxiliary valve body. If the accumulator piston pin comes out of either end of the auxiliary valve body the following conditions could occur.

1. Loss of DRIVE 2. Slipping in DRIVE 3. Burned forward and overrun clutches

DATE OF PRODUCTION CHANGE: (Figure No. 2) ------------------------- Beginning January 27, 1987 (Julian Date 027) all THM 700-R4 transmissions were produced with an auxiliary accumulator valve body assembly (Figure No. 1) that has a stepped bore at one end of the piston pin and a new cover with an oval instead of a round exhaust hole at the other end of the pin to retain the accumulator piston pin in place.

SERVICE ACTION:

The new auxiliary accumulator valve body (377) and cover (371) can be used on any 1987 THM 700- R4 transmission that has an auxiliary valve body (377).

NOTICE: If the accumulator piston pin has come out of the auxiliary valve body, check for burnt forward and overrun clutches.

SERVICE PARTS INFORMATION:

Part Number Description Models Affected ----------- ----------- --------------- 8663597 Auxiliary MRM, MXM, FAM, Accumulator MAM, MFM, MMM Valve Body Assembly

8667036 Auxiliary MCM, MTM, PRM, Accumulator TAM, TBM, YXM, Valve Body PCM, TJM, TKM, Assembly TNM, TRM, TUM, TXM 8667037 Auxiliary MDM, MHM, MLM, Accumulator MKM, MPM, MUM, Valve Body MWM, MZM Assembly

8667038 Auxiliary TSM, YAM, YDM, Accumulator YFM, YKM, YLM, Valve Body YMM, YNM, YPM, Assembly YSM, TYM, YZM

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.