LOOK ON THE RIGHT REAR CORNER OF THE TRANS OR THE TRANS FER CASE AND YOU WILL FIND WHAT LOOKS LIKE WHERE A SPEEDO CABLE GOES ON THIS IS THE SPEED SENSOR, EITHER IT CAN BE BAD OR THE MOST COMMON FAILURE ON THESE IS THE DRIVEN GEAR TAKE OUT THE ONE BOLT THAT HOLDS THE COLLAR ON AND PULL THE SPD SENSOR AND THE COLLAR AS AN ASSEMBLY AND CHECK THE GEAR IF IT IS OK YOU COULD HAVE A BAD SPD SENSOR ALLSO YOU SHOULD HAVE CHECK ENG LIGHT ON ,THE PT NO FOR THE GEAR IS 8971446590 IT COSTS ABOUT 30.00 JERRY