S10/T10 P/U 2WD L4-151 2.5L (1988)
Speedometer Gear, M/T: All Technical Service Bulletins
Speedometer Gear - Malfunctions
Number:
91-98-8C
Section:
8C
Dates:
October 1990
Corporate Bulletin No.: 067104
Subject:
MALFUNCTION OF THE SPEEDOMETER
DRIVE GEAR, DRIVEN GEAR AND/OR SPEEDOMETER
Model and Year:
1987-91 S1 (LLV POST OFFICE VEHICLES)
TO:
ALL CHEVROLET DEALERS
Some of the above postal vehicle chassis may experience a malfunction of the speedometer drive gear, driven gear, and/or speedometer adapter.
Effective January 24, 1990 with chassis' VIN 1GBCS10E2M2901183, a new driven gear was installed in production. The new driven gear can be
recognized visually as the following table illustrates.
GM PART #
COLOR
# OF TEETH
NEW
3987920
BLUE
20
OLD
3860347
YELLOW
24
IMPORTANT:
The new driven gear has eliminated the need for the speedometer adapter.
Recommended service procedures are outlined below:
Service Procedure # 1
1.
Remove and discard speedometer adapter (GM Part # 368025).
2.
Remove original speedometer driven gear and inspect for damaged teeth. If damaged, follow service procedure # 2. If it is not damaged, replace
the (yellow) 24 tooth driven gear with the (blue) 20 tooth driven gear (GM Part # 3987920).
For vehicles repaired under warranty use:
Labor Operation:
# T1611
Labor Time:
.3 hr.
FAILURE CODE:
92
NOTE:
The above procedures do not apply to 1991 Postal Vehicles (LLV) with L38 engines. Effective August 13, 1990 with chassis VIN
1GBCS10A0M2912017, a new engine (L38) and rear axle ratio (GU6) were installed in production. As a result of the axle ratio change, a
new driven gear is required. Use (gray) 22 tooth driven gear (GM Part Number 3987922) if vehicle is equipped with L38 and GU6.
Service Procedure # 2
1.
Remove and discard speedometer adapter.
2.
Remove driveshaft and rear transmission extension housing.
3.
Replace both speedometer drive and driven gear with:
Drive Gear (blue) GM Part
96040176
Driven Gear (blue) GM Part
3987920
NOTE:
The above procedures do not apply to 1991 Postal Vehicles (LLV) with L38 engines. Effective August 13, 1990 with chassis VIN
1GBCS10A0M2912017, a new engine (L38) and rear axle ratio (GU6) were installed in production. As a result of the axle ratio change, a