HARSH ENGAGEMENT CONDITIONS SYMPTOMS/DIAGNOSIS/REPAIRS

HARSH ENGAGEMENT CONDITIONS: I. PARK OR NEUTRAL TO DRIVE OR REVERSE II. REVERSE TO DRIVE - VEHICLES WITH 2.8L ENGINES ONLY

MODELS AFFECTED: 1987-88 6000, BONNEVILLE, AND GRAND PRIX --------------- EQUIPPED WITH THM 440-T4 (ME9)

BULLETIN COVERS:

Harsh engagement conditions and specific service information for 1987-88 models equipped with a THM 440-T4 transaxle. Other items which cause harsh engagement conditions are: - vacuum leaks (low vacuum supply to the vacuum modulator) 33-46 Cm Hg (13- 18 In Hg) required - stuck modulator valve - missing #9 checkball

DATE OF PRODUCTION CHANGE: (Figure 1) -------------------------

November 24, 1987 (Julian Date 328), all THM 440-T4 transaxles were built using a new 1-2 servo cushion spring, reverse servo cushion spring and reverse servo return spring.

SERVICE ACTION: (Figure 2) --------------

I. Harsh Engagement From Park Or Neutral To Drive Or Reverse - 1988 Bonneville Models

1. Remove the 1-2 servo assembly and the reverse servo assembly from the transaxle. 2. Disassemble and replace the 1-2 servo cushion spring (559) and the reverse servo cushion spring (549) with the correct part listed in the Service Parts Information section. 3. Install the 1-2 servo assembly and reverse servo assembly in the transaxle.

II. Harsh Engagement From Reverse To Drive, Park Or Neutral To Drive Or Reverse - 1987-88 6000 Models and 1988 Grand Prix Models With 2.8L Engines Only

1. Remove the 1-2 servo assembly and the reverse servo assembly from the transaxle. 2. Disassemble and replace the 1-2 servo cushion spring (559), the reverse servo cushion spring (549) and the reverse servo return spring (552) with the parts listed in the Service Parts Information section. 3. Install the 1-2 servo assembly and reverse servo assembly in the transaxle.

SERVICE PARTS INFORMATION: --------------------------

Part No. Description Usage -------- ----------- ------

8668121 Reverse Servo Cushion Spring (549) All 1987-88 Models

8668123 1-2 Servo Cushion Spring (559) All 1987-88 Models

8668127 Reverse Servo Return Spring (552) 1987-88 Vehicles W/ 2.8L Engines Only

SERVICE MANUAL REFERENCE:

Refer to the THM 440-T4 (ME9) Automatic Transaxle On Car Service section for appropriate service information.

SERVICE NOTES:

For warranty purposes, use both Labor Operations described below:

Labor Operation K6623 for the reverse servo assembly: 1987-1988 6000 Models - .5 Hour 1987-1988 Bonneville Models - .8 Hour 1988 Grand Prix Models - .8 Hour

Labor Operation K6626 for the 1-2 servo assembly: 1987-1988 6000, Bonneville Models - .5 Hour 1988 Grand Prix Models - 2.1 Hours

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.