What would cause a speedometer to be erratic? It does not move smoothly, instead it makes aprox 5 to 8 mph mini jumps when accelerating or decelerating. It responds to speed changes but indicates aprox 10 mph high @ 60mph along with the erratic movement.
Any ideas to fixing this?
99, 4.0, auto, 4x4
Thanks

 

Check the wiring and plug for the sender on the rear end.

 

Like the other guy said, however all I know is on a 95 explorer has a speed sensor and a small gear, the gear can wear out, however make sure to take old one with you to get a new one, cause in my friens case, there were 3 slightly different sizes!