SHUDDER ON LAUNCH (INSTALL NEW ENGINE MOUNT). GMC Truck GMC G Van 1994

SUBJECT: SHUDDER ON LAUNCH (INSTALL NEW FRONT ENGINE MOUNTS)

MODELS: 1992-94 CHEVROLET AND GMC TRUCK G1,G2 VANS WITH 4.3L ENGINE (VIN Z - RPO LB4)

CONDITION:

SOME OWNERS MAY EXPERIENCE A SHUDDER ON INITIAL LAUNCH. THIS CONDITION MAY OCCUR FROM 0-20 MPH ON A HARD ACCELERATION. THIS CONDITION MAY BE DUPLICATED BY BRAKE TORQUING THE ENGINE WITH FOUNDATION BRAKES.

CAUSE:

THE ENGINE MOUNT RUBBER COMPOUND IS DESIGNED TO COMPRESS DURING ENGINE START-UP AND ACCELERATION TO DAMPEN ENGINE VIBRATION/SHAKE. THE 2 TABS LOCATED ON THE MOUNT ARE USED FOR ASSEMBLY AIDS TO LOCATE ENGINE MOUNT IN PROPER POSITION DURING ASSEMBLY. ON A HARD ACCELERATION OR BRAKE TORQUE, THE RIGHT HAND ENGINE MOUNT COMPRESSES, BRINGING LOCATOR TABS TO A NEAR GROUND OUT CONDITION. THE RUBBER COMPOUND RATE IS TOO SOFT TO DAMPEN OUT THE SHUDDER ON LAUNCH.

CORRECTION:

INSTALL A NEW ENGINE MOUNT WITH A HIGHER RATED RUBBER COMPOUND.

SERVICE PROCEDURE:

REFERENCE SERVICE MANUAL, SECTION 6A3.

REMOVAL PROCEDURE:

NOTE: WHEN RAISING OR SUPPORTING THE ENGINE FOR ANY REASON, DO NOT USE A JACK UNDER THE OIL PAN, SHEET METAL, OR CRANKSHAFT PULLEY. DUE TO THE SMALL CLEARANCE BETWEEN THE OIL PAN AND OIL PUMP SCREEN, JACKING AGAINST THE OIL PAN MAY CAUSE POOR CLEARANCE BETWEEN PAN AND PUMP SCREEN, RESULTING IN DAMAGE TO THE OIL PUMP PICKUP UNIT.

1. SUPPORT ENGINE WITH SUITABLE SAFETY JACK STANDS. DO NOT LOAD THE ENGINE MOUNTING. 2. RAISE THE ENGINE ONLY ENOUGH FOR SUFFICIENT CLEARANCE TO REMOVE ENGINE MOUNT. CHECK FOR INTERFERENCE BETWEEN THE REAR OF THE ENGINE AND THE DASH PANEL FOR PROPER CLEARANCE FOR THE DISTRIBUTOR ASSEMBLY. POSSIBLE DISTRIBUTOR DAMAGE MAY RESULT IF ENGINE IS JACKED UP TOO HIGH. 3. REMOVE ENGINE MOUNT THROUGH-BOLT AND NUT. 4. REMOVE ENGINE MOUNT ASSEMBLY, BOLTS, NUTS, AND WASHERS.

INSTALLATION PROCEDURE:

1. INSTALL ENGINE MOUNT ASSEMBLY, BOLTS, NUTS, AND WASHERS. TORQUE FASTENERS TO PROPER SPECIFICATIONS. REFERENCE SERVICE MANUAL, SECTION 6A3. 2. INSTALL ENGINE MOUNT THROUGH-BOLT AND NUT. TORQUE FASTENERS TO PROPER SPECIFICATIONS. REFERENCE SERVICE MANUAL, SECTION 6A3. 3. LOWER ENGINE. REMOVE SAFETY STANDS AND LOWER VEHICLE.

SERVICE PARTS INFORMATION:

P/N DESCRIPTION QTY 22146241 ENGINE MOUNT ASSY. 2

PARTS ARE CURRENTLY AVAILABLE FROM GMSPO.

WARRANTY INFORMATION:

FOR VEHICLES REPAIRED UNDER WARRANTY, USE:

LABOR OP DESCRIPTION LABOR TIME J1507 ENGINE MOUNT REPLACE USE PUBLISHED LABOR OPERATION TIME

FIGURES: 0

CAPTIONS:

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.