For 1990-2009 cars

# NO GEARS/SLIPPING ALL RANGES STICKING REVERSE BOOST VALVE

#### MODELS AFFECTED: 1984 LIMOUSINES AND COMMERCIAL CHASSIS

Some 1984 Limousines and Commercial Chassis equipped with THM 400 transmissions which were built between February 1, 1984, and March 31, 1984, may experience a loss of operation in all forward and reverse ranges or slipping in all ranges. Refer to the chart below for model and serial number applications affected.

Trans. Vehicle Model Serial Number Range ------- ----- -------------------- Limousine AN 1790 to 2139 Commercial Chassis AD 1230 to 1434

This condition may result from a mislocated forward clutch snap ring and/or some clutch seals positioned out of their seats due to 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 1, Items "A" and "B", for examples.

If the reverse boost bushing is like letter "A", the bushing and valve must be replaced. Install service package P/N 8625902 which contains the following:

1 - Regulator Boost Valve Bushing 1 - Regulator Boost Valve

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.