just bought a 97 F150 XLT 4x4. 4.6 automatic. the speedometer will max out completely at 100 mph by the time I am going 30. scan tool shows the VSS reading the same speed that is shown on the speedometer. getting a P0720 for the output shaft sensor. have replaced the speed sensor on the side of the transmission near the shift linkage, and the sensor on the tail shaft of the transfer case. nothing has changed at all it does seem to shift a little erratically, but is very drivable. the speedometer moves up and down smoothly, doesnt jump around or anything. im stumped......a bad wire or connection should result on no function at all.......or so i would think.... please steer me in the right direction.

 

odometer does not work either, however this may be a mechanical failure inside the odometer itself. the reset button is spongy and doesn't do anything to the trip meter. truck does appear to have been modified in any way. transfer case looks like it may have been removed at some point, but everything looks proper.....

 

It's probably the cluster. You might need to have it worked on.