INFO ON DIAG OF TRANS NOISE,DELAYED, ENGAGED. GMC Truck Yukon

SUBJECT: INFORMATION ON DIAGNOSIS OF TRANSMISSION NOISE, DELAYED ENGAGEMENT, DELAYED/BUSY SHIFTS AND NO DRIVE OR REVERSE

MODELS: 1997 CHEVROLET GMC C/K, G, P TRUCKS 1997 ISUZU 1997 AM GENERAL 1997 REUMECH ERMETEK WITH HYDRA-MATIC 4L80E TRANSMISSION (RPO MT1)

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FIELD REPORTS HAVE INDICATED THAT A DENTED OIL PAN CAN CAUSE ANY OF THE FOLLOWING CUSTOMER CONCERNS: - WHINE NOISE IN 1ST AND/OR 2ND GEAR THAT APPEARS TO BE A GEAR WHINE, - WHINE NOISE IN ALL GEARS THAT APPEARS TO BE AN OIL PUMP OR TORQUE CONVERTER WHINE, - GRIND OR GROWL NOISE IN 1ST GEAR, - DELAYED ENGAGEMENT FROM PARK TO REVERSE OR DRIVE, - DELAYED OR NO SHIFTS TO ANY GEAR, - NO FORWARD OR REVERSE GEARS, - BUSY SHIFTS IN AND OUT OF 4TH GEAR AND/OR TCC, - SLIPPING AND/OR TRANSMISSION OVERHEATING.

WHEN DIAGNOSING ANY OF THE ABOVE LISTED TRANSMISSION CONCERNS, REMOVE THE TRANSMISSION OIL PAN AND INSPECT THE INSIDE BOTTOM OF THE OIL PAN FOR A "WITNESS MARK" WHERE THE OIL FILTER INLET MAY HAVE BEEN CONTACTING THE OIL PAN. IF THE OIL FILTER HAS BEEN CONTACTING THE OIL PAN, REPLACE THE OIL PAN AND THE OIL FILTER. THE OIL PAN GASKET IS REUSABLE. IF THE CONCERN IS NOT CORRECTED, REFER TO THE APPROPRIATE SERVICE MANUAL FOR FURTHER DIAGNOSIS.

THE OIL PAN CAN BE DENTED/DAMAGED BY LIFTING THE TRANSMISSION ASSEMBLY WITH THE OIL PAN. DO NOT PLACE ANY SPACERS, WEDGES, OR OBJECTS SMALLER THAN THE OIL PAN BETWEEN THE TRANSMISSION JACK AND THE OIL PAN. DAMAGE TO THE OIL PAN CAN RESTRICT OIL FLOW TO THE OIL FILTER PICKUP AND CAUSE OIL PUMP CAVITATION, LOW LINE PRESSURE, NOISE AND/OR TRANSMISSION FAILURE.

FIGURES: 01 ATTACHMENTS: 00

Object Number: 169917 Size: FS

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.