I have a 2003 F-350 6.0L and my speedo jumps from 0-90 and it'll work fine for a little then lets say i'm going 55 it'll jump from 40-70 which i'm not too worried about but the main problem is it seems to be bucking every once in a while and i pulled up to a stop light today and it just stalled on me it mainly does it when i'm crusing about 60 then it'll buck and kill the cruise control. I believe its the rear end speed sensor does that sound right or somebody shed some light here.

Thank you
Steve R

 

The speed sensors are a common failure on all SuperDuties. I've replace two on my V10 and one had been replaced on my 6L. They actually get smashed by rocks etc... The symptoms sound like they could be caused by the speed sensor, but I don't know about the stalling? Mind you, if the tranny thinks your doing 60 and you're actually parked, then it would probably stall on you. I think I paid $30 cdn for one from the dealer. The other thing you might want to check is your transmission range sensor. It can cause all kinds of problems like that as well.