The speedometer on my 97 F150 keeps fluctuating badly while I am driving, sometimes it moves something like between 30 and 40 when I am within that speed, other times though it will jump all the way down to 0 when I am doing about 40. Does anybody have any suggestions? I am really confused on this one.

 

After I got my lift mine started doing that as well, though I also have bad vibration at lower speeds as well so I figure they are related. Won't know if it will be solved until I get my new driveline on Tuesday. Are you getting any vibration or anything with the fluctuation? Otherwise perhaps just a loose cable or something I would guess. However, I am just stabbing in the dark.

 

This is the PRE-'97 forum. Your '97 truck isn't pre-'97, and its speedo works very differently from these older trucks'.