NO GEARS/SLIPPING ALL RANGES STICKING REVERSE BOOST VALVE

MODELS: 1984 C, K, P, G WITH THM 400 TRANSMISSION

Some 1984 THM 400 transmissions built between February 1, 1984, and March 31, 1984, may experience a no drive condition or slippage in all ranges. Refer to the chart for model and serial number applications affected.

When servicing any 1984 THM 400 transmission which is listed in the chart and exhibits the above condition, you may find either the forward clutch snap ring mislocated or out of its seat and some seals out of their seat.

If these conditions are found, they may be caused by a sticking reverse boost valve in the reverse boost bushing. It is very important to visually inspect the reverse boost bushing which is located in the oil pump assembly for possible mismachining of the inner diameter. Refer to Figure No. 1, examples "A" and "B".

If the reverse boost bushing is like example "A", the bushing and valve must be replaced. Order service package 8625902 which contains the following.

Service Package 8625902 contains:

1 - Regulation Boost Valve Bushing 1 - Regulator Boost Valve

Model Serial Numbers Model Serial Number ----- -------------- ----- ------------- FA 9745 to 12760 FP 9960 to 12837 FB 8498 to 11466 FQ 1714 to 1860 FC 1027 to 1051 FR 1069 to 1119 FD 7065 to 9425 FT 1255 to 2050 FE 1003 to 1004 FV 8735 to 12185 FF 3610 to 4254 FW 11270 to 14565 FH 1701 to 2057 FX 1949 to 2146 FJ 6335 to 7739 FY 1608 to 1833 FK 1136 to 1401 FZ 1178 to 1225 FM 34782 to 47400 MF 43420 to 49554 FN 2372 to 2873

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.