A/T - Harsh 1-2 Gear Shift

88pontiac11

Bulletin Number: 88-7-36
Reference Number: 877134
Publish Date: 7/88
1-2 SHIFT DURING COLD WEATHER
Subject: SERVICE AND PARTS INFORMATION ON NEW 1-2 ACCUMULATOR PISTON

Models 1988 6000, SUNBIRD, GRAND AM AND LeMANS
Affected: EQUIPPED WITH THM 125/125C (MD9)

FIGURE 2:

A New 1-2 Accumulator Piston (421) and Seal (420) 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 hard P.T.F.E.. 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 pistion seal has a resemblance to the new (rubber) seal (420). Refer to Bulletin 87-7-43 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.

FIGURE 1 - THM 125/125C TRANSAXLE IDENTIFICATION INFORMATION:

DATE OF PRODUCTION 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 S.O.P. 89 for Windsor built THM 125/125C transaxles.

FIGURE 2:

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:

^ The new seal must be used with the new piston.
^ The previous seal must be used with the previous piston.

NOTICE: 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:

Part No. Description

8665920
Package 1-2 Accumulator Piston (421) and Seal (420)
8665807
Seal 1-2 Accumulator (Rubber) (420)
8631895

Seal 1-2 Accumulator (P.T.F.E.)

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.