FIRM/HARSH 1-2 SHIFT INFORMATION

MODELS AFFECTED: Grand Prix, Bonneville, Parisienne, Parisienne Wagon

Some 1983 and 1984 THM 200-4R transmissions (Models BT, BY, BQ and OM) may experience a condition relating to the above subject.

Beginning in February 1984, the parts in the service packages listed below went into production to correct these conditions.

Subject I. Firm or Harsh 1-2 Shift

Use the following service package for transmission models BT and BY.

Service Package: 8639912

1 - Control Valve Body Assembly 1 - Intermediate Servo Cushion Spring 1 - 1-2 Accumulator Piston Spring 1 - Pressure Regulator Valve Spring 1 - Control Valve Body Spacer Plate 1 - Instruction Sheet

Service Procedure:

Remove the following parts and replace them with the parts contained in the above service package.

1. Control Valve Body Assembly 2. Intermediate Servo Cushion Spring 3. 1-2 Accumulator Piston Spring 4. Pressure Regulator Valve Spring 5. Control Valve Body Spacer Plate 6. 3-4 Accumulator Piston Spring

NOTE: The 3-4 Accumulator Piston Spring Item #6 above is to be removed and discarded. The 3-4 accumuZator piston is to be aseembZed as shown in Figures 1 and 2.

Subject II. Soft or Slipping 1-2 Shift

Use the following service package for transmission models BQ and BM.

Service Package 8639914 for the BQ Model Transmission

1 - Control Valve Body Assembly 1 - 3-4 Accumulator Spring

Service Package 8639915 for the OM Model Transmission

1 - Control Valve Body Assembly 1 - 3-4 Accumulator Spring

Service Procedure:

Remove the control valve body assembly and the 3-4 accumulator spring from the transmission and replace with the control valve body assembly and the 3-4 accumulator spring provided in the appropriate service package.

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.