HARSH OR FIRM 2-3 UPSHIFTS DIAGNOSIS AND REPAIR

MODELS AFFECTED: 1986 SRTA UNITS, AND 1987 CENTURYS, LESABRES, ELECTRAS, AND RIVIERAS EQUIPPED WITH A THM 440-T4 HYDRA-MATIC 4T60 TRANSAXLE AND 3.8L ENGINE (VIN CODE 3)

BULLETIN COVERS: (Figure 1) ---------------- A harsh or firm 2-3 upshift that may occur most noticeably under 112 throttle acceleration on 1986 SRTA models and 1987 Centurys, Electras, Rivieras, and LeSabres equipped with a 3.8L and THM 440-T4/Hydra-matic 4T60 transaxle. This condition can be corrected by following the procedure listed under "Service Action".

SERVICE ACTION:

1. Verify correct minimum and maximum pressures.

2. Check for vacuum leaks and/or a low vacuum supply to the vacuum modulator. Required vacuum is 44-61 KPa (13-18 in. Hg.). The vacuum signal should respond quickly to throttle movement; if not, check for anything that could cause a vacuum restriction to the modulator causing a delayed response to throttle movement, like paint in the modulator tube and/or carbon at the throttle body fitting.

3. Remove the 3-4 M.T.V. Bushing (338), 2-3 Accumulator Valve (337), then the 2-3 Accumulator Spring (336) as shown in Figure 2. Install the 2-3 Accumulator Spring (336) from the appropriate service package shown in the "Service Parts Information" section. While the transaxle is disassembled, check the items listed below that affect transaxle operation which may also contribute to the harsh shift condition.

- #7 Check Ball and Capsule for leaks. - 1-2 Servo Pipe for leaks. - 1-2 Servo for seal damage or binding. - #12 Check Ball missing, or mislocated. - Spacer Plate for peening from Check Balls #4 and #12.

SERVICE PARTS INFORMATION:

Transaxle Model 2-3 Accumulator Identification Spring Package (Figure 1) Number Contents ------------ ------ -------- 6FBH, 7FBH, 8662972 (1) Spring, 2-3 Accumulator 7FKH (2) Spacer Plate Gaskets (1) Instruction Sheet

6FCH, 6FZH 8662973 (1) Spring, 2-3 Accumulator 7FCH, 7FZH (2) Spacer Plate Gaskets (1) Instruction Sheet

6FTH, 6FYH 8662977 (1) Spring, 2-3 Accumulator 7FNH, 7FRH, (2) Spacer Plate Gaskets 7FTH (1) Instruction Sheet

Parts are currently available from GMSPO.

SERVICE MANUAL REFERENCE:

Refer to the appropriate 1986 or 1987 Service Information Manual, Section 7Al Automatic Transaxle On Car Service and THM 440-T4/HYDRA-MATIC 4T60 (ME9) Automatic Transaxle Unit Repair Table of Contents for Control Valve Assembly service information.

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.