A/T - New Low and Reverse Clutch and Plate Dimensions
90chevy08GMC NUMBER: 90-7A-54
GROUP: 7A Manual Transmission
DATE: April, 1990
CORPORATE
NUMBER: 077107R
SUBJECT: NEW LOW AND REVERSE CLUTCH SUPPORT AND SELECTIVE PLATE DIMENSIONS
MODELS: ALL 1990 TRUCKS AND VANS W/4L60 (700-R4)
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 - THM 700-R4/HYDRA-MATIC 4L60 Transmission Identification Information:
DATE OF PRODUCTION CHANGE:
(See Figure 1)
Production changes occurred in two phases which are shown below.
Figure 2 - Measuring Low And Reverse Clutch Support:
SERVICE INFORMATION:
In most cases, the new low and reverse clutch assembly will only require a fifth reaction plate instead of a selective plate. 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 the 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.
SERVICE MANUAL REFERENCE:
Refer to the HYDRA-MATIC 4L60/THM 700-R4 Automatic Transmission Unit Repair section of the
appropriate Service Manual for removal and installation information.