COLD START RATTLE NOISE. Buick Regal 1994

REVISION: 12/16/96

THIS BULLETIN IS BEING REVISED TO ADD MODELS AND 1996-97 MODEL YEARS. PLEASE DISCARD CORPORATE BULLETIN 57-71-06 (SECTION 7 - TRANSMISSION). ----------------------------------------------------------------------

SUBJECT: COLD START RATTLE NOISE (DIAGNOSIS/SERVICE PROCEDURE)

MODELS: 1991 BUICK REATTA 1991-96 BUICK RIVIERA 1991-96 BUICK PARK AVENUE, ULTRA 1991-97 BUICK REGAL 1992-97 BUICK LE SABRE 1994-96 BUICK CENTURY 1994-97 BUICK SKYLARK 1991-93 CADILLAC ELDORADO, SEVILLE, SIXTY SPECIAL AND FLEETWOOD (FWD) 1991-95 CADILLAC DE VILLE 1991-97 CHEVROLET LUMINA 1992-96 CHEVROLET LUMINA APV 1997 CHEVROLET VENTURE 1994-95 CHEVROLET BERETTA, CORSICA 1995-97 CHEVROLET MONTE CARLO 1991-92 OLDSMOBILE TORONADO, TROFEO 1991-95 OLDSMOBILE NINETY EIGHT 1991-97 OLDSMOBILE CUTLASS SUPREME 1992-97 OLDSMOBILE EIGHTY EIGHT, SILHOUETTE 1994-96 OLDSMOBILE CUTLASS CIERA 1994-97 OLDSMOBILE ACHIEVA 1991-97 PONTIAC GRAND PRIX 1992-97 PONTIAC BONNEVILLE, TRANS SPORT 1994-97 PONTIAC GRAND AM WITH HYDRA-MATIC 4T60-E (RPO M13)

CONDITION:

SOME OWNERS MAY NOTICE A RATTLE NOISE FROM THE ENGINE COMPARTMENT AFTER A COLD START THAT LASTS FOR LESS THAN ONE MINUTE. THIS CONDITION WILL USUALLY ONLY OCCUR ONCE PER DAY AFTER THE VEHICLE IS STARTED AFTER SITTING OVERNIGHT OR AN EXTENDED PERIOD OF TIME.

CAUSE:

THIS RATTLE NOISE MAY BE ASSUMED TO BE AN ENGINE RELATED NOISE (PISTON SLAP, BEARING KNOCK, LIFTER RATTLE, ETC.) BUT MAY ACTUALLY BE A 4T60-E TRANSAXLE NOISE CAUSED BY A COMBINATION OF OIL PUMP STARVATION/ CAVITATION AND PRESSURE REGULATOR VALVE INSTABILITY. THIS TRANSAXLE NOISE CONDITION DOES NOT DAMAGE THE TRANSAXLE AND DOES NOT CAUSE A DURABILITY CONCERN. THIS TRANSAXLE NOISE CONDITION IS MORE NOTICEABLE WITH ENGINES THAT EXHIBIT A "FAST" START (SHORT CRANK TIMES AND IMMEDIATE ENGINE RPM INCREASE AFTER START). THE 3.1L ENGINE (VIN M - RPO L82) IS A GOOD EXAMPLE OF A "FAST" STARTING ENGINE, THOUGH OTHER 4T60-E/ENGINE COMBINATIONS MAY EXHIBIT THIS NOISE ALSO.

CORRECTION:

IF THE DIAGNOSTIC STEPS LISTED UNDER SERVICE PROCEDURE LEAD TO THE 4T60-E TRANSAXLE AS THE CAUSE OF THE COLD START RATTLE NOISE, NO REPAIRS SHOULD BE ATTEMPTED. THERE IS NO REPAIR FOR THIS NOISE CONDITION AT THIS TIME. THIS BULLETIN WILL BE UPDATED WHEN A REPAIR BECOMES AVAILABLE. REFER TO THE WARRANTY INFORMATION FOR DIAGNOSIS ALLOWANCE.

SERVICE PROCEDURE:

1. CHECK FOR A DISCONNECTED TRANSAXLE MODULATOR VACUUM LINE (THIS COULD CAUSE EXCESSIVE TRANSAXLE OIL PUMP NOISE).

2. RAISE THE VEHICLE ON A HOIST.

3. REMOVE THE FLYWHEEL DUST SHIELD(S) AND REMOVE THE TORQUE CONVERTER FLYWHEEL BOLTS.

4. POSITION THE TORQUE CONVERTER AS FAR AWAY FROM THE FLYWHEEL AS POSSIBLE (USUALLY NO MORE THAN 7 MM (1/4 IN)). IT MAY BE HELPFUL TO USE A PIECE OF WIRE LOOPED AROUND A TORQUE CONVERTER LUG AND A LOOSENED BOTTOM PAN BOLT. THIS WILL HOLD THE TORQUE CONVERTER AWAY FROM THE FLYWHEEL.

5. LOWER THE HOIST AND ALLOW THE VEHICLE TO SIT A MINIMUM OF SIX HOURS (PREFERABLY OVERNIGHT).

6. START THE VEHICLE AND LISTEN FOR THE COLD START RATTLE NOISE. THIS COULD BE PERFORMED WITH THE OWNER, IF POSSIBLE.

- IF THE COLD START RATTLE NOISE IS STILL PRESENT, THE CONDITION IS CAUSED BY THE ENGINE AND THIS BULLETIN NO LONGER APPLIES. REFER TO SECTION 6 OF THE SERVICE MANUAL FOR ENGINE NOISE SYMPTOM DIAGNOSIS.

- IF THE COLD START RATTLE NOISE IS NOT PRESENT, THE CONDITION IS CAUSED BY THE TRANSAXLE AND NO REPAIRS SHOULD BE ATTEMPTED. REFER TO THE WARRANTY INFORMATION FOR DIAGNOSIS ALLOWANCE.

WARRANTY INFORMATION:

FOR VEHICLES DIAGNOSED UNDER WARRANTY, USE:

LABOR OPERATION LABOR TIME

K6101 2.0 HOURS

IMPORTANT: THIS LABOR OPERATION SHOULD ONLY BE USED WHEN DIAGNOSIS LEADS TO A NON-REPAIRABLE TRANSAXLE NOISE AS COVERED IN THIS BULLETIN.

FIGURES: 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.