RATTLE AFTER TCC LOCK-UP REPLACE TORQUE CONVERTER. GMC Truck S15 Pickup - 2WD 1991

For 1990-2009 cars

# RATTLE AFTER TCC LOCK-UP REPLACE TORQUE CONVERTER

#### SUBJECT: TORSIONAL RATTLE AFTER TORQUE CONV. LOCKUP (REPLACE TORQUE CONVERTER)

#### MODELS: 1991-92 S-TRUCKS WITH 2.5L ENGINE (L38) AND 4L60 AUTOMATIC TRANSMISSION

Owners of some 1991-92 S-trucks with 2.5L engines (RPO L38) and automatic transmissions (4L60) may experience a torsional rattle noise after the 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 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.

The Torque Converter must be replaced with a revised Torque Converter (P/N 08686969), if the rattle/vibration stops when:

1. Light brake application is made (To unlock the TCC), OR

2. The vehicle downshifts to 3rd gear.

#### 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

Labor Time: 2.9 hrs.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.