HARSH 1-2 UPSHIFTS ALL GEARS. GMC Truck Yukon

SUBJECT: HARSH 1-2 UPSHIFT OR HARSH UPSHIFTS ALL GEARS (REPROGRAM PCM/VCM)

MODELS: 1997-98 CHEVROLET AND GMC C/K, G, P TRUCKS 1997-98 AM GENERAL WITH 6.5L DIESEL ENGINE (VINS F, S, Y - RPOS L65, L56, L57) AND HYDRA- MATIC 4L80E TRANSMISSION (RPO MT1)

CONDITION:

SOME OWNERS MAY COMMENT ON HARSH TRANSMISSION UPSHIFTS FROM FIRST TO SECOND GEAR OR HARSH TRANSMISSION UPSHIFTS IN ALL GEARS.

CAUSE:

CONDITION MAY BE DUE TO SOFTWARE CALIBRATION THAT ALLOWS THE SHIFT ADAPTS TO MODIFY LINE PRESSURE AND MAINTAIN THE MAXIMUM ADAPTABLE LINE PRESSURE.

CORRECTION:

IF NORMAL DIAGNOSIS DOES NOT PROVIDE A CORRECTION, REPROGRAM THE PCM/VCM WITH THE APPROPRIATE CALIBRATION 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.

PARTS INFORMATION:

NEW CALIBRATION VERSION BROADCAST CODE FILE NUMBER

16268055 1998 CD ROM DISC 6 CFXZ 16268065 1998 CD ROM DISC 6 CFYA 9353135 1998 CD ROM DISC 6 CKCJ 9353145 1998 CD ROM DISC 6 CKCK 9353165 1998 CD ROM DISC 6 CKCM 9352795 1998 CD ROM DISC 6 CJRY 9352805 1998 CD ROM DISC 6 CJRZ 9353195 1998 CD ROM DISC 6 CKCR 9353225 1998 CD ROM DISC 6 CKCS 9353255 1998 CD ROM DISC 6 CKCW 9353275 1998 CD ROM DISC 6 CKCY 9353285 1998 CD ROM DISC 6 CKCZ 9352265 1998 CD ROM DISC 6 CJDR 9353175 1998 CD ROM DISC 6 CKCN 9353185 1998 CD ROM DISC 6 CKCP 9353245 1998 CD ROM DISC 6 CKCU 9361785 1998 CD ROM DISC 6 CLTH 9353235 1998 CD ROM DISC 6 CKYT 9354995 1998 CD ROM DISC 6 CLDX 9355005 1998 CD ROM DISC 6 CLDY 9355015 1998 CD ROM DISC 6 CLDZ 9355045 1998 CD ROM DISC 6 CLFC 9355145 1998 CD ROM DISC 6 CLFR 9355055 1998 CD ROM DISC 6 CLFD 9355065 1998 CD ROM DISC 6 CLFF 9355075 1998 CD ROM DISC 6 CLFH 9355085 1998 CD ROM DISC 6 CLFJ 9355115 1998 CD ROM DISC 6 CLFM 9355125 1998 CD ROM DISC 6 CLFN

THE NEW CALIBRATIONS ARE AVAILABLE STARTING WITH THE CD ROM 1998 DISC 6 UPDATE.

WARRANTY INFORMATION:

FOR VEHICLES REPAIRED UNDER WARRANTY, USE:

LABOR OPERATION: J6355 ON-CAR

USE PUBLISHED LABOR OPERATION TIME.

FIGURES: 00 ATTACHMENTS: 00

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.