A/T - Torsional Rattle After TCC Lockup

Number: 92-317-7A
Section: 7A
Date: OCT. 1992
Corporate Bulletin No.: 267104
ASE No.: A2

Subject:
TORSIONAL RATTLE AFTER TORQUE CONVERSION CLUTCH LOCKUP

Model and Year:
1991-92 S TRUCKS WITH 2.5L ENGINE (L38) AND 4L60 AUTOMATIC TRANSMISSION

Owners of some 1991-1992 S-trucks with 2.5L engines (RPO L38) and automatic transmissions (4L60) may experience a torsional rattle noise after the [1][2]Torque Converter Clutch locks up. The condition is usually in the 45-55 mph range and when under light acceleration.

The torsional rattle may be due to incorrect spring rate on the damper springs in the torque converter. The result is a bottoming-out condition in the torque converter damper assembly.

Torsional rattle occurs under the following condition:

1. Vehicle must be in 4th gear.
2. The [1][2]torque converter clutch must be locked in.
3. The Vehicle speed must be between 45-55 MPH.
4. The Vehicle is under a light acceleration.

Once the condition is created if the rattle/vibration stops when:

1. Light brake application is made (To unlock the TCC), OR
2. The vehicle downshifts to 3rd gear

The Torque Converter must be replaced with a revised Torque Converter (P/N 08686969).

VEHICLES INVOLVED:

Identification of vehicles can be made by noting the Julian date on the 4L60 automatic transmission. Vehicles with Julian date AFTER 086 are NOT affected.

SERVICE PARTS INFORMATION:

Part
Number Description
08686969 Torque Converter

Parts are currently available from GMSPO.

WARRANTY INFORMATION:

For vehicles repaired under warranty use:

Labor Operation: K7020

Use applicable labor time guide for labor hours.