HARSH OR FIRM 3-4 UPSHIFT GENERAL INFORMATION (4T60E)

TRANSMISSION APPLICATIONS: SUBJECT:

HYDRA-MATIC 4T60E (M13) HARSH OR FIRM 3-4 UPSHIFTS (GENERAL INFORMATION)

TRANSMISSION MODELS: VEHICLE APPLICATIONS: 2ABW, 2ANW, 2AWW 1992 OLDSMOBILE C CAR, BUICK C CAR, CADILLAC C CAR

Bulletin Covers: Refer to Figures 1 ----------------------------------- Some early model 1992 transaxles used in 1992 C-Cars built between Julian Date 182 (July 1, 1991) through Julian Date 234 (August 22, 1991) were built with a three spring pack in the 3-4 accumulator cannister. It was determined that the third spring may contribute to a harsh or firm 3-4 upshift (this condition may become more noticeable at high altitudes). This condition can be corrected by following the procedure listed under Service Action.

Service Action: (Figures 2 & 3) ------------------------------- 1. Verify correct minimum and maximum line pressure readings (use the line pressures procedure as outlined in Figure 2).

2. Check for vacuum leaks and/or low vacuum supply to the vacuum modulator (NOTE: Altitude will affect engine vacuum readings). The vacuum signal should respond quickly to throttle movement. If not, find the cause of the vacuum restriction and correct.

3. Remove channel plate (401) and disassemble the 3-4 accumulator cannister (421). Verify the transaxle was built with a two spring accumulator pack. If the 3-4 accumulator cannister contains a third spring, remove the outer most 3-4 accumulator spring (423) and reassemble.

While the transaxle is disassembled, check the items listed below which also affect the quality of the 3-4 shift.

* Check-ball #10 missing or mislocated

* Control valve assembly (300) for stuck 3-4 accumulator valve (350)

Service Manual

Refer to the appropriate Service Manual section for proper disassembly and assembly procedures.

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.