MUFFLER TONE QUALITY (DIAG./ INSTALL RETURNED MUFFLER)

SUBJECT: L35 MUFFLER TONE QUALITY

MODEL and YEAR: 1992 S/T TRUCKS WITH 4.3L (L35) ENGINES

Owners of some 1992 S/T Utility vehicles with 4.3L CPI engines (L35) built before the VIN breakpoints listed below may comment on louder than normal exhaust noise. A retuned muffler is currently available which will reduce the amount of audible noise.

VEHICLES INVOLVED:

Pontiac West Assembly Plant:

Built Before VIN

1GNCT18W8N0151461

Moraine Assembly Plant:

Built Before VIN

1GNDT13W4N2204849

SERVICE PROCEDURE:

Removing Exhaust Parts

CAUTION:

Always wear protective goggles and gloves when removing exhaust parts as falling rust and sharp edges from worn exhaust components could result in serious personal injury.

Using a penetrating oil on the threads of U-bolts can assist in the removal of the exhaust components.

Installing Exhaust Parts

When installing a new muffler and tailpipe, on any model, check for proper alignment. Rattles and noise vibrations in the exhaust system are usually caused by a misalignment of parts. When aligning the system, leave all bolts or nuts loose until all parts are properly aligned, then tighten, working from the front to rear. Exhaust system hangers, hanger brackets, and clamps which are damaged should be replaced to maintain exhaust system alignment. Refer to S-10 Blazer Service Manual section 6F Exhaust System for additional information.

SERVICE PARTS INFORMATION

Part Number Description ----------- ----------- 12541384 Muffler - 2 Dr. and 4 Dr. Blazer

15662532 Tailpipe - 2 Dr. Blazer

15662531 Tailpipe - 4 Dr. Blazer

15595048 Clamp - 2 Dr. and 4 Dr. Blazer

Parts are currently available from GMSPO.

WARRANTY INFORMATION

For vehicles repaired under warranty use:

Labor Operation: L2584

Use applicable labor time for labor hours.

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.