NEW PARKING LOCK SYSTEM FOR HEAVIER GROSS VEHICLE WEIGHT

MODELS AFFECTED: 1990 4T60 TYPE TRANSMISSIONS (THM440T4)

CHANGE TO ASSEMBLY COMPONENTS (Figures 1 - 4)

To expand model usage that includes vehicles with a heavier Gross Vehicle Weight (GVW), a new parking lock system will be used in the production of all 1990 transaxle models for the 1990 Century, Electra Park Avenue, Riviera, LeSabre, and Regals equipped with a HYDRA-MATIC 4T60 (THM 440-T4). For this change to be implemented, the following parts were modified:

Actuator guide is now wider by 0.65mm (0.026") for the increased thickness of the parking lock actuator assembly. The pawl lockout plunger assembly and spring are eliminated. Now, there is no need for a slot for the plunger to ride in; therefore, the slot has been eliminated. The "O" ring (bushing/actuator guide) seal is now larger to accommodate the increased thickness of the actuator guide. (Figure 1)

The parking lock actuator assembly "bullet" is now 1.77mm (0.070") wider. The overall length of the new assembly is now 13.8mm (0.543") longer than the previous assembly. (Figure 2)

Transaxle case bore for the actuator guide is now wider by 0.65mm (0.026") to accommodate the wider actuator guide. (Figure 3)

The parking pawl lockout pin has been eliminated from the final drive parking lock pawl and the effective length reduced about 1.0mm (0.039") from bullet to parking gear because of the wider actuator "bullet". (Figure 4)

IMPORTANT: The new parking lock system will not service past models, unless ALL the components are replaced including the transaxle case. The transaxle case, parking lock actuator assembly, parking lock pawl and actuator guide are not interchangeable with models built before September 25, 1989 (Julian Date 268).

DATE OF PRODUCTION CHANGE

Starting September 25, 1989 (Julian Date 268), all HYDRA-MATIC 4T60 (THM 440-T4) will be built with the new parking lock system.

SERVICE PROCEDURE

The new parking lock system will assemble the same way as the previous parking lock system.

SERVICE PARTS INFORMATION

Model Part Number Description Year Model Usage ----------- ----------- ---- ----------- 8668985 Case - Transaxle (Common) 1990 All Except OLAH 8668986 Case - Transaxle 1990 OLAH 8675325 Guide and Seal Assembly 1990 All 8675335 Actuator Assembly, Parking Lock 1990 All 8675330 Gear Asm., Final Drive Internal 1990 All

Parts are expected to be available on 12-15-89. 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 canceled as incorrectly ordered while the 400 control is in place.

SERVICE MANUAL REFERENCE

Refer to the appropriate 1990 Service Information Manual for service procedures.

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.