MANUAL TRANSMISSION RATTLE NOISE AT IDLE. GMC Truck GMC K Pickup

REVISION: 01/27/97

THIS BULLETIN IS BEING REVISED TO ADD THE 1992-95 MODEL YEARS AND CHANGE PART NUMBERS. PLEASE DISCARD CORPORATE BULLETIN NUMBER 66-72-02 (SECTION 7 - TRANSMISSION). ---------------------------------------------------------------------- REVISION: 02/20/97

THIS BULLETIN IS BEING REVISED TO CHANGE A LABOR OPERATION NUMBER. PLEASE DISCARD CORPORATE BULLETIN NUMBER 66-72-02A (SECTION 7 - TRANSMISSION).

---------------------------------------------------------------------- SUBJECT: MANUAL TRANSMISSION RATTLE NOISE AT IDLE (INSTALL CONVENTIONAL FLYWHEEL)

MODELS: 1992-96 CHEVROLET AND GMC C/K 2-3 MODELS WITH 6.5L DIESEL ENGINE (VIN'S F, P - RPO'S L65, L49) AND NV4500 5 SPEED MANUAL TRANSMISSIONS (RPO'S MW3, MT8)

CONDITION:

SOME OWNERS MAY COMMENT ABOUT A RATTLE OR BANGING NOISE FROM THE TRANSMISSION WHILE THE ENGINE IS IDLING, THE CLUTCH ENGAGED (CLUTCH PEDAL RELEASED) AND THE TRANSMISSION IS IN NEUTRAL. THIS CONDITION IS MORE LIKELY TO OCCUR ON A VEHICLE THAT IDLES FOR PROLONGED PERIODS OF TIME. THIS RATTLE SHOULD NOT BE CONFUSED WITH NORMAL ROLL- OVER NOISE (TURNING BEARING/WHIRRING NOISE) WHICH IS GENERATED WHILE THE TRANSMISSION IS IN NEUTRAL, CLUTCH ENGAGED AND ENGINE IDLING.

CAUSE:

FAILURE OF THE HYSTERESIS DAMPER INSIDE THE DUAL MASS FLYWHEEL (DMF).

CORRECTION:

INSTALL A CONVENTIONAL FLYWHEEL, REVISED CLUTCH KIT AND A TRANSMISSION DAMPER. THESE REVISED PARTS ARE CURRENTLY INSTALLED IN 1997 MODEL TRUCKS.

IMPORTANT: INSTALLATION OF THESE PARTS WILL RESULT IN SOME DRIVE RATTLE (TRANSMISSION GROWL) WHEN DRIVING AT ABOUT 900 RPM OR LESS. NORMAL DMF SHUT-DOWN RATTLE WILL BE ELIMINATED IF THE CLUTCH IS DISENGAGED (PEDAL DEPRESSED), BUT RATTLE WILL OCCUR IF THE ENGINE IS SHUT-OFF WITH THE TRANSMISSION IN NEUTRAL AND THE CLUTCH ENGAGED (FOOT OFF PEDAL). THIS RATTLE IS FROM THE TRANSMISSION AND CAN NOT BE ELIMINATED BY TRANSMISSION REPAIR OR REPLACEMENT.

SERVICE PROCEDURE:

REFER TO THE APPROPRIATE YEAR SERVICE MANUAL SECTION 7C FOR CLUTCH REPLACEMENT PROCEDURES. WHEN INSTALLING THE NEW FLYWHEEL, THE RETAINING RING FROM THE DMF IS NOT USED.

4-WHEEL DRIVE: THE DAMPER IS INSTALLED BETWEEN THE TRANSMISSION AND THE TRANSFER CASE. TO INSTALL THE DAMPER, THE TRANSMISSION REAR EXTENSION HOUSING MUST BE REMOVED. REFER TO THE APPROPRIATE YEAR UNIT REPAIR MANUAL, SECTION 7B8, NV4500 MANUAL TRANSMISSION FOR DETAILS. WHEN INSTALLING THE DAMPER NUT, APPLY LOCTITE(R) 242, P/N 12345493, TO THE NUT THREADS AND TORQUE THE NUT TO 325 LB. FT. (441 N.M).

2-WHEEL DRIVE: THE DAMPER IS PART OF THE YOKE ASSEMBLY. REPLACEMENT OF THE YOKE IS REQUIRED. TO INSTALL THE YOKE, REFER TO THE APPROPRIATE YEAR UNIT REPAIR MANUAL, SECTION 7B8, NV4500 MANUAL TRANSMISSION. WHEN INSTALLING THE YOKE/DAMPER NUT, USE LOCTITE(R) 242, P/N 12345493, ON THE NUT THREADS AND TORQUE THE NUT TO 325 LB. FT. (441 N.M).

IMPORTANT: YOKE/DAMPER NOT USED ON 15,000 LB. MODELS

THE FOLLOWING FASTENER TIGHTENING SPECIFICATIONS SHOULD BE USED: -REAR EXTENSION-TO-CASE BOLTS 40 LB. FT. (54 N.M) -FLYWHEEL-TO-CRANKSHAFT BOLTS 65 LB. FT. (90 N.M) -PRESSURE PLATE-TO-FLYWHEEL BOLTS 25 LB. FT. (35 N.M)

NOTICE: THIS TRANSMISSION REQUIRES A SPECIAL SYNTHETIC LUBRICANT, P/N 12346190. DO NOT SUBSTITUTE ANY OTHER LUBRICANT AS INTERNAL TRANSMISSION DAMAGE MAY RESULT. TRANSMISSION CAPACITY IS 4 QUARTS (3.78L).

PARTS INFORMATION

P/N DESCRIPTION QTY 12375179 '92-95 K L49/L65 FLYWHEEL KIT 1 12375180 '92-95 C L49/L65 FLYWHEEL KIT 1 12375181 '96 K L49/L65 FLYWHEEL KIT 1 12375182 '96 C L49/L65 FLYWHEEL KIT 1 14061685 PILOT BEARING 1 12345493 THREAD LOCK SEALANT A/R 12346190 MANUAL TRANSMISSION FLUID 4

PARTS ARE CURRENTLY AVAILABLE FROM GMSPO.

WARRANTY INFORMATION:

FOR VEHICLES REPAIRED UNDER WARRANTY, USE:

LABOR OPERATION DESCRIPTION LABOR TIME J1420 FLYWHEEL, MANUAL TRANSMISSION-REPLACE USE PUBLISHED K2160 TRANSMISSION YOKE, REPLACE (C) LABOR OPERATION K2764 TRANSMISSION REAR HOUSING, R & R (K) TIME

IMPORTANT: LABOR OPERATION IS CODED TO BASE VEHICLE COVERAGE IN THE WARRANTY SYSTEM.

FIGURES: 0 CAPTIONS: 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.