Speedometer problem
 

Hoping someone can help me out with this problem. The speedometer on my 1992 Dodge has worked when it wanted to for a while, it may work for a few days or a few hours, today it was just jumping around and the would work for a few minutes then drop to 30 MPH and back to 70 and then to 0, so I disconnected the sender at the transfer case and hooked up a drill to the square shaft and spun it as fast as the drill would run booth directions and the speedometer registered nothing, never moved, so I hooked it back up and took it back out on the road and the thing worked but with the same problem as before.

What I would like to know is why wouldn't it register when I spun it up with the drill. And anyone have any ideas how to fix the problem.
Thanks for any help.

what about the sensor !

Not sure what you're referring to as a sensor. I thought that was what I had my drill hooked up to?

So you hooked the drill to the cable end that runs towards the gauge cluster? If so, and you so no movement then either the drill wasn’t spinning fast enough OR you may have a broken gear in the cluster that runs the speedometer.

My truck’s speedometer would work intermittently so I changed the VSS on the side of the transfer case and that didn’t solve it. I took a closer look at the inside of the square hole that the VSS slides into and the hole was rounded out instead of being square.

I had to use some epoxy putty and filled the end of the square hole up and then reinserted the VSS shaft and allow it to set up for a minute or so then removed it. I then let the epoxy cure and once cured I reassembled everything and it worked perfectly.

So, basically the problem was the VSS shaft was intermittently slipping within the “rounded out” square hole

I'll have to try with another drill, was using my battery drill and its not a high rpm drill. Didn't know how fast it needed to be spun.
But when I hooked it back up to the transfer case the speedometer worked again, but still intermittently.

Also check or replace the pig tail wiring that hooks to the VSS, the movement of the wiring under the truck can eventually cause the wires to break inside the casing.

Next thing I'll try.