Bonneville V6-231 3.8L VIN 3 SFI (1988)
Band: Customer Interest
A/T - Harsh Engage, Double Bump or Shudder
Bulletin Number:
90-7-40
Reference Number:
077119R
Publish Date:
5/90
Subject:
HARSH ENGAGE, DOUBLE BUMP OR SHUDDER-PARK/ NEUTRAL TO REVERSE - NEW REV. BAND MATERIAL
Models
Affected:
1984-90 ALL MODELS WITH 440T4 TRANSMISSION
This bulletin has been revised to add information about the rubber torsional dampen unit. See "Important" under "Bulletin Covers" and the first sentence
of "Service Procedure".
This bulletin supersedes 89-7-4 issued 10/88. Please discard bulletin 89-7-4.
BULLETIN COVERS:
A new reverse band assembly that will help decrease harsh engagement, double "bump" or shudder from park or neutral to reverse in a vehicle equipped
with a HYDRA-MATIC 4T60 (THM 440-T4) transaxle. The new reverse band assembly has new friction material that will help decrease reverse
engagement concerns.
Reverse engagement concerns can be caused by "oxidized" fluid (the fluid may visually appear to be OK), "glazed" (overheated) reverse band assembly
friction material and/or improper surface finish on the drum of the 2nd clutch housing.
IMPORTANT:
Harsh reverse engagement could also be caused by a worn or damaged rubber torsional damper unit (on models so
equipped) that is incorporated as part of the right hand drive axle shaft. Refer to section 4D of the Service Manual.
SERVICE PROCEDURE:
Check engine idle speed, engine/transaxle mounts, rubber torsional damper unit for the rigbt hand drive axle shaft (on models so equipped) and transaxle
reverse line pressure following Service Manual procedures. If okay, replace the reverse band assembly and 2nd clutch housing drum and bushing
assembly with the appropriate parts listed below in "SERVICE PARTS INFORMATION".
DATE OF PRODUCTION CHANGE:
Starting February 07, 1990 (Julian Date 038) all HYDRA-MATIC 4T60 (THM 440-T4) transaxles will be built with the new reverse band assembly.
SERVICE PARTS INFORMATION:
Parts are expected to be available for part number 8675152 on 06-15-90. 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.
Parts are currently available from GMSPO for part numbers 8661912 and 8668958.
SERVICE MANUAL REFERENCE:
Refer to the HYDRA-MATIC 4T60 (THM 440-T4) Automatic Transaxle Unit Repair and On-Vehicle sections in the appropriate model year service
manual for repair procedures.
