VIBRATION AT HIGHWAY SPEED. Pontiac Firebird 1996

SUBJECT: VIBRATION AT HIGHWAY SPEED (REPLACE PROPELLER SHAFT)

MODELS: 1993-96 CHEVROLET CAMARO 1993-96 PONTIAC FIREBIRD WITH 5.7L V8 ENGINE (VIN P - RPO LT1)

CONDITION:

SOME OWNERS MAY EXPERIENCE A VEHICLE VIBRATION AT HIGHWAY SPEEDS. WHEN MEASURED AT THE DRIVER'S SEAT TRACK, THIS VIBRATION WILL BE A 1ST ORDER DRIVELINE FREQUENCY. THE SAME VIBRATION CAN BE CONFIRMED AT THE AXLE PINION NOSE AND AT THE REAR EXTENSION HOUSING OF THE TRANSMISSION.

IMPORTANT: WHEN MEASURING VIBRATION FREQUENCY ON A HOIST, THE REAR OF THE VEHICLE MUST BE SUPPORTED BY THE AXLE TUBES IN ORDER TO MAINTAIN THE PROPER VEHICLE TRIM HEIGHT. THIS WILL PREVENT VIBRATION DUE TO EXCESSIVE DRIVELINE ANGLE. ALSO, ANY VIBRATION DUE TO EXCESSIVE DRIVELINE ANGLE WILL APPEAR AS 2ND ORDER DRIVELINE FREQUENCY VIBRATION.

CAUSE:

FIRST ORDER DRIVELINE VIBRATION MAY BE CAUSED BY BEAMING BETWEEN THE ENGINE AND TRANSMISSION.

CORRECTION:

A PREVIOUSLY RELEASED PROPELLER SHAFT IS AVAILABLE TO ADDRESS THE HIGHWAY SPEED VIBRATION CONDITION. THIS REDUCED MASS PROPELLER SHAFT IS CONSTRUCTED OF ALUMINUM LESS A PINION DAMPER.

VERIFY CONDITION PER ABOVE NOTE THAT THE VIBRATION IS 1ST ORDER DRIVELINE DISTURBANCE; PREFERABLY USING AN ELECTRONIC VIBRATION ANALYZER (EVA).

OTHER CONDITIONS SUCH AS EXCESSIVE DRIVELINE ANGLE DIFFERENCE MAY PRODUCE 2ND ORDER DRIVELINE VIBRATION CONCERNS. THE PROPER PROCEDURES TO MEASURE AND CORRECT FOR EXCESSIVE DRIVELINE ANGLE CONDITION ARE NOT SHOWN IN THE CURRENT SERVICE MANUAL. CONSULT A 1992 SERVICE MANUAL FOR THE PROPER PROCEDURE. THE FRONT AND REAR PROPELLER SHAFT ANGLE MUST BE LESS THAN ONE DEGREE OF EACH OTHER.

IMPORTANT: DUE TO THE REMOVED DAMPER, THE ALTERNATE PROPELLER SHAFT MAY UNMASK EXISTING REAR AXLE NOISE. A LIGHTER PROPELLER SHAFT WILL REDUCE VIBRATION BUT WILL POSSIBLY UNMASK AXLE NOISE, WHILE A HEAVIER PROPELLER SHAFT WILL MASK AXLE NOISE BUT MAY CAUSE VIBRATION. THIS INHERENT CONDITION IS ALWAYS THE TRADEOFF. IT IS SUGGESTED THAT THE VEHICLE BE TEST DRIVEN TO EVALUATE AXLE NOISE BEFORE AND AFTER PARTS ARE INSTALLED.

INSTALL ALTERNATE PROPELLER SHAFT, PART NUMBER 10085375.

WARRANTY INFORMATION:

FOR VEHICLES REPAIRED UNDER WARRANTY, USE:

LABOR OPERATION: F1280 USE PUBLISHED LABOR OPERATION TIME.

FIGURES: 0 ATTACHMENTS: 0

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.