Thanks for the replies. I have changed the sensor on the rear end, the sensor on the tranny, tried another speedo with no change the speedo still bouncing and the o/d light is flashing. I also checked my speedo on another truck and is working perfectly. So i'm perplexe now. Where is the problem? From the PCM? The wiring? NEED MORE HELP . THANKS GUYS

E-150 1999 V-6 4.2L (analog speedo and odo)

 

Do you have 4 wheel ABS on that monster? If so there may be another speed sensor, or it may be in the ABS module.

 

O/D light flashing indicates there is a code in the processor. Retreive the code and see if that gives you a clue to the problem. Was the sensor in the rear end damaged physically? If so you may have some missing teeth on the reluctor that may give you a poor signal to the speedometer and pcm.

 

I have only rear ABS on that monster and somebody told me if i resolve the speedo problem it migth resolve the tranny problem too.

 

I forgot there was no physical damage on the sensor only a little metal shaving, so i open the rear end to look at ring and everything was normal but a little worn on the two side gears

 

Pull the codes, the transmission has stored a code. You need to see what it is. It's possible that just have a bad ground, check your battery cables and make sure that you have a good ground to the frame, engine, and body.