UNDESIRED UPSHIFTER OR DOWN. BETWEEN 2ND AND 3RD GEAR. GMC Truck GMC P52 RV/Van Chassis 1997

SUBJECT: UNDESIRED UPSHIFT OR DOWNSHIFT BETWEEN SECOND AND THIRD GEAR WHEN MANUALLY SHIFTED TO FIRST GEAR (NEW CALIBRATION)

MODELS: 1997 CHEVROLET AND GMC P TRUCKS WITH A 4.3L ENGINE (VIN W - RPO L35) AND A 4L80E (MT1) AUTOMATIC TRANSMISSION

VIN BREAKPOINTS:

PLANT YEAR DIVISION MODEL PLANT CODE FROM THROUGH 1997 CHEVROLET P32 DETROIT "3" V3301486 V3303289 1997 GMC P32 DETROIT "3" V3500001 V3500318

CONDITION:

SOME OWNERS MAY COMMENT ON UNDESIRED TRANSMISSION SHIFTS.

UNDESIRED SHIFTS MAY INCLUDE ANY OF THE FOLLOWING SCENARIOS: 1. THE TRANS WILL NOT DOWNSHIFT TO FIRST GEAR AT SPEEDS GREATER THAN 25 MPH (40 KMPH) WHEN MANUALLY SHIFTED TO FIRST GEAR. 2. THE TRANS WILL UPSHIFT TO SECOND GEAR AT 30 MPH (48 KMPH) WHEN THE SELECTOR LEVER IS IN MANUAL FIRST GEAR. 3. THE TRANS WILL NOT DOWNSHIFT TO SECOND GEAR AT SPEEDS ABOVE 40 MPH (64 KMPH) WHEN MANUALLY SHIFTED TO FIRST GEAR OR SECOND GEAR. 4. THE TRANS WILL UPSHIFT TO THIRD GEAR AT SPEEDS ABOVE 40 MPH (64 KMPH) WHEN THE SELECTOR LEVER IS IN MANUAL FIRST OR MANUAL SECOND.

CAUSE:

IMPROPER VCM CALIBRATION.

CORRECTION:

TO CORRECT THIS CONDITION, DEALERS ARE TO REFLASH THE VCM WITH THE APPROPRIATE PART NUMBER LISTED BELOW.

SERVICE INFORMATION DO NOT ATTEMPT TO ORDER THE SOFTWARE/CALIBRATIONS FROM GMSPO. THEY ARE PROGRAMMED INTO THE VEHICLE'S PCM/VCM VIA A TECHLINE TOOL DEVICE.

SERVICE PARTS INFORMATION

NEW CALIBRATION VERSION FILE NUMBER 16216183 CD ROM 1996 DISC 22 16216184 CD ROM 1996 DISC 22 16216185 CD ROM 1996 DISC 22 16216186 CD ROM 1996 DISC 22 16216187 CD ROM 1996 DISC 22 16216188 CD ROM 1996 DISC 22

THIS NEW CALIBRATION IS AVAILABLE STARTING WITH THE CD ROM 1996 DISC 22 UPDATE.

WARRANTY INFORMATION FOR VEHICLES REPAIRED UNDER WARRANTY, USE:

LABOR OPERATION LABOR TIME J6352 OFF-CAR USE PUBLISHED J6355 ON-CAR LABOR OPERATION TIME

FIGURES: 0 ATTACHMENTS: 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.