I have a 96 ford f250 7.3L diesel. My speedometer likes to bounce when it shows im going 50-55 MPH when im really going about 70 mph. This is also causing my cruise control not to work. Ive tried a lot of things from new VSS that didn't work I'm kinda at a dead end on what to do.

 

change the vss in the rear end.it send the info to the speedo.

 

That is my next step is to go to my local ford dealer ship and order one cause the one i bought from oreillys made it was worse.

 

make sure the gear that the sensor reads in the rear end isn't bad or full of metal