YOU NEED A DIFFERENT SPEEDO DRIVEN GEAR THE ONE THAT DRIVES THE ENG (VEH) SPEED SENSOR AND THEN YOU CAN GET IT TOO WITHIN ABOUT 3 MILES PER HOUR OF BEING DEAD ON, AND IT WILL GET THE TRANS BACK TO SHIFTING WHERE IT SHOULD , LEAVE THE TRANS CONTROL SW TURNED ON TO PWR DRIVE AND IT SHOULD BE FINE , MY TROOPER HAS THE SAME SIZE TIRES ON IT AND HAS THE TRANS POWER LITE ON FOR THE LAST 80000 MILES AND IT SHIFTS FINE TOWING A CAMP TRAILER , YOU NEED A 15 TOOTH DRIVEN GEAR AND THE SMALLEST ISUZU HAS IS A 16 TOOTH , A 15 TOOTH WOULD PUT YOU DEAD ON, JERRY