NEW TRANSAXLE I.D. CODES INFO. ON NEW OVERHAUL PACKAGES

Model and Year: 1989-90 A, W CAR WITH THM 440-T4 TRANSMISSION

TO: ALL CHEVROLET DEALERS

A change of the 3rd clutch plate fiber (640) material requires that all 1989 and 1990 transaxle models built after Julian Date (076) March 17, 1989, have new calibrations and new two letter (alpha) model codes. A new overhaul package and 3rd clutch plate assembly package will service the new 1989 and 1990 models.

Models built after Julian date (076) March 17, 1989, have the new model codes and contain a new spacer plate (031) (most models), 3-2 control spring (341), 2-3 accumulator spring (336), 1-2 servo cushion spring (559) (all models except AA, AB and AF) and the new 3rd clutch plate assembly (640). The updated valve body assembly will have an update level laser etched into the casting by the servo pipes (note service information for valve body I.D. and new spacer plate information - figure 3).

SERVICE PROCEDURE:

When replacing the 3rd clutch fiber plates (640) on 1989 or 1990 models for any reason, check the two-letter model code on the tag as shown in Figure 1.

IMPORTANT: Order Overhaul packages, 3rd clutch plate assembly packages and valve body assemblies by the model code for all early 1989 models, and the new 1989 and 1990 models. Reference chart, Figure 2.

When servicing a Hydra-matic 4t60 transaxle you may notice: the new 3rd clutch plates may have the following markings as shown in figure 4. The new 3rd clutch plates may have four black stripes about an 1/8" wide and the notch may not be in one of the teeth. Some early build models after Julian Date (076) will have some of the markings or none at all.

IMPORTANT: THE FOLLOWING CONDITIONS COULD OCCUR IF PARTS ARE MIXED.

1. Harsh shifts or potentially a tie-up condition (worse in altitudes) on 2-3 and 3-2 shifts if the old 3rd clutch plates are installed into a transaxle built after the Julian Date (076) (with new model codes).

2. A slip-bump condition on 2-3 and 3-2 shifts if the new 3rd clutch plates are installed into a transaxle built before Julian Date (076) (old model codes).

SERVICE PARTS INFORMATION:

Part Number Description Model Year - Model Usage ----------- ----------- ------------------------ 8662990 3rd Clutch Plate 1989/1990 - See New Models Assembly Package Listed in Figure 2

8662989 Overhaul Package 1989/1990 - See New Models Listed in Figure 2

Parts are expected to be available (for part numbers 8662990 and 8662989) on 07-17- 89. Until then, normal part orders will not be accepted by GMSPO. Only verifiable emergency VIP orders will be accepted. SPO will make every effort to obtain parts. All parts will be placed on 400 control to waive VIP surcharges. However, the part will be shipped premium transportation at dealer's expense. All other order types will be cancelled as incorrectly ordered while the 400 control is in place.

When the supply of old style 3rd clutch plate assemblies (both 3rd clutch plates and overhauls) is depleted the new style 3rd clutch plates and an instruction sheet will be available. The instruction sheet will show which calibration update kit to order for each model built after Julian Date (076).

SERVICE MANUAL REFERENCE:

Refer to the appropriate 1989 Service Manual.

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.