R 10 P/U 2WD V8-379 6.2L DSL (1988)
Governor: All Technical Service Bulletins
A/T - New Governor Driven Gear for No Upshift or Erratic
Number:
88-161-7A
Section:
7A
Date:
MARCH, 1988
Subject:
ERRATIC OR NO UPSHIFT - NEW
GOVERNOR DRIVEN GEAR
Model and Year:
1987-88 VEHICLES WITH THM 400/475
OR THM 700-R4 TRANSMISSIONS
FIGURE 2 - "APPLECORED" GOVERNOR DRIVEN GEAR
TO:
ALL CHEVROLET DEALERS
A THM 400/475 or THM 700-R4 transmission with an erratic or no upshift condition may be created by "applecoring" of the governor driven gear.
"Applecoring" is pictured in the illustration below.
A new governor driven gear with a higher fiberglass content entered production on all THM 400/475 transmissions December 11, 1987 (Julian date
345). THM 700-R4 transmissions were produced with a new gear beginning July 6, 1987 (Julian date 187).
"Applecoring" of the governor driven gear may be the result of nicks or burrs present on the output shaft drive gear. Inspection of the output shaft should
be performed and if nicks or burrs are present the output shaft should be replaced.
The new service part numbers are listed below for each model transmission.
Part No.
Description
8663995
THM 700-R4 - Governor Driven Gear and Pin
Package
8629977
THM 400 - Governor Driven Gear and Pin Package
