1-1 SHIFT DURING COLD WEATHER NEW ACCUMULATOR PISTON - P/N

1988 FIRENZA, CUTLASS CALAIS AND CUTLASS CIERA MODELS EQUIPPED WITH 125C TRANSAXLE (RPO MD9)

A new 1-2 accumulator piston (421) and seal (420) have been developed for vehicles equipped with a THM 125C transaxle to increase shift consistency during vehicle operation in cold weather conditions. The groove bottom on the 1-2 accumulator piston where the seal is located is flat and the new piston seal is now made of a soft rubber instead of a harder material. (Refer to Figure 2.)

Some vehicles equipped with a 1987 THM 125C built between the dates of April 13, 1987, through April 21, 1987 (Julian dates 103-112), may have a rolled or misassembled 1-2 accumulator piston seal, resulting in a possible harsh 1-2 shift. This piston seal has a resemblance to the new (rubber) seal (420). Refer to bulletin 87-T-48 for additional information. If replacement of this seal built between April 13, 1987, through April 21, 1987 (Julian dates 103-112), is necessary, the new 1-2 accumulator piston (421) and seal (420) must be used.

Date of Product Change: (Refer to Figure 1) -------------------------------------------

May 18, 1988 (Julian date 139), the new 1-2 accumulator piston and seal went into production for all Willow Run built THM 125/125C transaxles. Future production changes are scheduled for start of production 1989 for Windsor built THM 125/125C transaxles.

Service Action: (Refer to Figure 2) -----------------------------------

The new 1-2 accumulator piston and seal can be used on any 1980 through 1988 THM 125C transaxle as a complete assembly. The previous 1-2 accumulator piston is no longer available for service use. If replacement of the 1-2 accumulator piston seal is necessary, use the following guidelines.

o The new seal must be used with the new piston.

o The previous seal must be used with the previous piston.

NOTE: Do not attempt to mix parts or delayed and extended shift conditions will occur.

Service Parts Information:

When ordering parts to service the 1-2 accumulator assembly, use the following part numbers:

Package No. Description ---------- -----------

8665920 Package 1-2 Accumulator Piston (421) and New Seal (420) 8665807 Seal 1-2 Accumulator (New Soft Rubber) (420) 8631895 Seal 1 -2 Accumulator (Old Type Hard Material)

Service Manual Reference:

Refer to the THM 125 (MD9) automatic transaxle unit repair section of your service manual whenever replacement of the 1 -2 accumulator piston and seal is necessary.

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.