i have a 2000 dodge 2500 diesel automatic 2wd cruise control system. the speedometer quit working and now it wont shift gears. checked fuse and speed sensor at the transmission. still wont work.electronic speed system, not mechanical. NEED ADVICE ON WHAT COULD BE WRONG!! thanks

 

Check the speed sensor on the rear diff.

 

if that doesnt work what should i try next? if you can then just give me everything i can do to find the problem. thanks