CLUTCH CHATTER/ LAUNCH SHUDDER NEW DESIGN CLUTCH DRIVEN DISC

TRANSMISSION APPLICATIONS: SUBJECT: 6.2L OR 5.7L AND 4 AND 5 CLUTCH CHATTER/SHUTTER ON LAUNCH SPEED M/T (NEW DESIGN CLUTCH DRIVEN DISC)

TRANSMISSION MODELS: VEHICLE APPLICATIONS: 88-90 C/K WITH 6.2L OR 5.7L AND 4 AND 5 SPEED M/T

Bulletin Covers:

Some 1988 - 90 C/K trucks equipped with 5.7L and 6.2L engines with 4-speed and 5-speed manual transmissions may experience a condition of chatter or shudder on launch. Revised clutch discs and matching pressure plates have been released for these vehicles and are available through CANSPO. The installation of these parts will provide significant improvement in the involved vehicles.

DATE OF PRODUCTION CHANGE

Revised pressure plates were installed shortly after the start of the 1990 model year. Revised clutch discs will be installed at the start of the 1991 model year.

SERVICE PROCEDURE:

1988 OR 1989 MODEL

The pressure plate and clutch disc should be replaced at the same time as the parts have been designed to work together.

1990 MODEL:

These vehicles should require a new clutch disc only. However, when the pressure plate is removed inspect the cover for a manufacturers name stamp. If the name Valeo appears on the pressure plate cover the pressure plate is of the revised design and does not need replacement unless damaged.

If the name Borg and Beck appears on the pressure plate cover the pressure plate assembly requires replacement. Only very early Production 1990 vehicles may be equipped with Borg and Beck pressure plates.

Refer to section 7C of the appropriate Service Manual for clutch disc and pressure plate replacement procedure.

SERVICE PARTS INFORMATION

PRESSURE CLUTCH ENGINE TRANSMISSION PLATE P/N DISC P/N ------ ------------ --------- ---------

5.7L 5 SPEED 15638388 15668525 5.7L 4 SPEED 15638388 15668526 6.2L 4 SPEED 15638388 15668525

Parts are currently available through CANSPO.

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.