NEW OUTPUT SHAFT/BEARING & 3RD ROLLER CLUTCH ASSEMBLY

Models Affected: 1990 6000, BONNEVILLE AND GRAND PRIX MODELS W/4T60

BULLETIN COVERS: (Figures 1 and 2)

New output shaft/bearing and 3rd roller clutch assembly for increased lubricant flow. The new parts were designed to help keep the 3rd roller clutch and input sprag assemblies running cooler when over-running. For this change to be implemented, the following parts were modified:

The new output shaft bearing with only a single row of needle bearings instead of a double row. This makes for an easier path for the oil flow to the 3rd roller clutch and input sprag assemblies.

The 3rd roller clutch outer race will have four less lube holes. The four lube holes are in line with the very end of the rollers. See Figure 2. Eliminating these holes helps keep the rollers from skewing or the edge of the rollers from dipping into the lube hole when overrunning, generating increased heat.

IMPORTANT: Do not try to modify the previous style parts to the new style; this may cause durability concerns.

SERVICE PROCEDURE:

Use the new output shaft/bearing and new 3rd roller clutch assembly for an obvious increased heat concern of the 3rd roller clutch or input sprag assemblies. This would include distortion of the plastic cage for the 3rd roller clutch and/or a blue race of the input sprag.

The new parts will assemble the same way as the previous parts. The new output shaft and bearing will service previous models back to the 1988 model year change for the longer output shaft required for the larger differential side gears and larger differential pinions gears in the final drive assembly. Refer to Service Bulletin HM 88-52 (Corp. Ref. No. 877132). The new 3rd roller clutch assembly will service all 1989 and 1990 models that have been equipped with an input housing thrust bearing assemblv. Refer to Service Bulletin 897440-06 (Corp. Ref. No. 977109).

DATE OF PRODUCTION CHANGE:

Starting December 11, 1989 (Julian Date 345) all HYDRA-MATIC 4T60 (THM 440-T4) transaxles are built with the new 3rd roller clutch assembly.

Starting January 25, 1990 (Julian Date 025) all HYDRA-MATIC 4T60 (THM 440-T4) transaxles are built with the new output shaft/bearing.

SERVICE PARTS INFORMATION:

Part No. Description Package Contents Model Year/Model Usage -------- ---------------------------- ---------------------- 8668990 Package, Output Shaft and Refer to Service Bearing Procedure

8675032 Bearing, Input Sun Gear/ " " Output Shaft

8677016 Roller Assembly Complete, " " 3rd Clutch

Part numbers 8668990 and 8675032 are expected to be available on 4-16-90. Part number 8677016 is expected to be available on 5-28-90. 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 canceled as incorrectly ordered while the 400 control is in place.

SERVICE MANUAL REFERENCE:

Refer to the appropriate Service Information Manual, Section 7A1 Automatic Transaxle On-Car Service and HYDRA-MATIC 4T60 (THM 440-T4) Unit Repair Section.

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.