A/T - New Low/Reverse Clutch Support Dimensions
90chevy19Number: 90-223-7A
Section: 7A
Date: April 1990
Corp. Bulletin No.: 077107
Subject: NEW LO AND REVERSE CLUTCH SUPPORT AND SELECTIVE PLATE DIMENSIONS
Model and Year: 1990 B, F, Y CARS AND ALL TRUCKS AND VANS WITH 4L60 (700-R4) AUTOMATIC TRANSMISSION
THIS BULLETIN CANCELS AND SUPERSEDES DEALER SERVICE BULLETIN NO. 90-166-7C. THE PART NUMBER HAS BEEN CORRECTED FOR THE NEW LO AND REVERSE CLUTCH AND SUPPORT ASSEMBLY. ALL COPIES OF 90-166-7C SHOULD BE DISCARDED.
This bulletin covers a dimensional change in the low and reverse clutch support and its selective plates. The thickness of the low and reverse clutch support has increased while the thickness of the selective plates has decreased. Three selective plates are available.
Figure 1:
Production changes occurred in two phases which are shown below. (See Figure 1.)
Date Part Change Implemented
November 1, 1989 Low and Reverse Clutch Support
(Julian Date 305)
February 2, 1990 Selective Plates
(Julian Date 033)
In most cases, the new low and reverse clutch assembly will only require a fifth reaction plate instead of a selective plate.
Figure 2:
The only way to identify the new low and reverse clutch support is to measure its thickness with a micrometer. (See Figure 2.)
The new low and reverse clutch support and selective plates may be used to service some past model year transmissions if:
- Transmission was built after February 9, 1987 (Julian Date 040).
NOTICE: The SELECTIVE PLATES are not interchangeable between the previous clutch support and the new clutch support. If selective plates are installed in the wrong clutch assembly, durability of the low and reverse clutch will be reduced.
NEW LOW AND REVERSE CLUTCH ASSEMBLY:
PREVIOUS LOW AND REVERSE CLUTCH ASSEMBLY:
Parts are currently available from GMSPO.
Refer to the HYDRA-MATIC 4L60/THM 700-R4 Automatic Transmission Unit Repair section of the appropriate Service Manual for removal and installation information.