A/T - Parking Lock System For Heavier Vehicles
90buick01Bulletin 90-7440-1
Date Nov., '89
Ref. No. 90-036-7440
Corp. Ref. No. 977154
SUBJECT: NEW PARKING LOCK SYSTEM FOR HEAVIER GROSS VEHICLE WEIGHT (GVW) VEHICLES
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:
Figure 1:
^ Actuator guide is now wider by 0.65 mm (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)
Figure 2:
^ The parking lock actuator assembly "bullet" is now 1.77 mm (0.070") wider. The overall length of the new assembly is now 13.8 mm (0.543") longer than the previous assembly. (Figure 2)
Figure 3:
^ Transaxle case bore for the actuator guide is now wider by 0.65 mm (0.026") to accommodate the wider actuator guide. (Figure 3)
Figure 4:
^ The parking pawl lockout pin has been eliminated from the final drive parking lock pawl and the effective length reduced about 1.0 mm (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.