SERVICE MANUAL UPDATE-NEW SOLENOID ASSEMBLY/WIRING HARN.

MODELS: 1988 C/K, R/V, S/T, AND G VANS EQUIPPED WITH THM 70OR4 AUTOMATIC TRANSMISSION

TRANSMISSION MODELS: MAM, MDM, MFM, MKM, MLM, MPM, MRM, MWM, MXM, MZM, THM, TJM, TKM, TLM, TUM, TXM

BULLETIN COVERS:

Introduction of a new Solenoid Assembly and Wiring Harness (Type 18) and new Control Valve Assembly for some 1988 THM 700-R4 models (refer to models listed above). The new control valve assembly uses a plug in place of the 4-3 pulse switch. The function of tbe 4-3 pulse switch, to momentarily release the torque converter clutch during a 4-3 downshift, was programmed into tbe ECM for the 1988 model year. These models bad previously used a Type 15 Solenoid Assembly.

DATE OF PRODUCTION CHANGE: (Figure No. 1) ------------------------- On April 20, 1988 (Julian Date 111), the 1988 THM 700-R4, THM and TLM models were built with the new Type 18 Solenoid Assembly and Wiring Harness. Beginning May 9, 1988 (Julian Date 130), the remaining 1988 THM 700-R4 models listed above were built using the new Type 18 Solenoid Assembly.

SERVICE NOTES:

Any 1988 THM 700-R4 transmission models built with tbe Type 18 Solenoid Assembly, refer to models and Julian Dates listed above, must be serviced with the Type 18 Solenoid Assembly and Wiring Harness Complete listed under "Service Parts Information". Any 1988 THM 700-R4 transmission model built with a Type 15 Solenoid Assembly may be serviced with the new Type 18 assembly; however, there will be no wire connection for the 4-3 pulse switch. The 4-3 pulse switch, which can be left installed, will then function as a plug.

SERVICE PARTS INFORMATION:

Part No. Description ------- ----------- 10478100 Type 18 Solenoid Assembly - Complete 8654415 Type 15 Solenoid Assembly - Complete

Parts are currently available from GMSPO.

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.