SMU-SECTION 6-ENG MECH CRANKSHAFT. GMC Truck GMC P42 Commercial Chassis 1997

SUBJECT: SERVICE MANUAL UPDATE - SECTION 6 - ENGINE MECHANICAL - CRANKSHAFT AND BEARINGS INSTALLATION

MODELS: 1997 CHEVROLET AND GMC P MODELS WITH 6.5L DIESEL ENGINE (VIN Y - RPO L57, MECHANICAL FUEL INJECTION ONLY) ALL BUILT ON OR AFTER MARCH 20, 1997

THE CRANKSHAFT BEARING UPPER BEARING INSERTS ON JOURNALS 1 AND 2 HAVE BEEN CHANGED. THEY DO NOT HAVE HOLES TO PROVIDE OIL FLOW TO THE OIL SPRAY NOZZLES AS NATURALLY ASPIRATED ENGINE MODELS DO NOT NEED OIL SPRAY COOLING ON THE FRONT CYLINDERS. THESE ARE THE SAME CRANKSHAFT BEARING UPPER BEARING INSERTS USED ON PRIOR MODEL YEAR NON-OIL SPRAY NOZZLE ENGINES. THIS WILL ELIMINATE OIL SPRAY COOLING OF PISTONS 1, 2, AND 3.

L57 ENGINE ASSEMBLIES (MECHANICAL FUEL INJECTION ONLY) BUILT ON OR AFTER MARCH 20, 1997, AND ALL L57 GMSPO LONG BLOCKS (TARGET ENGINES), HAVE INCORPORATED THESE CHANGES IN PRODUCTION. FOR ENGINES BUILT PRIOR TO MARCH 20, 1997, IF THERE IS A CONCERN THAT REQUIRES THE CRANKSHAFT TO BE REMOVED FROM THE ENGINE (REBUILD OR REPAIR), REFER TO CRANKSHAFT AND BEARING REPLACEMENT IN THE 1997 SERVICE MANUAL TO REPLACE THE CRANKSHAFT BEARING UPPER BEARING INSERTS ON JOURNALS 1 AND 2. ORDER BEARING INSERTS FOR A 1996 6.5L DIESEL ENGINE THROUGH GMSPO.

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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.