l8000 speedometer help needed

I have been working on the speedometer because it only seems to work when it wants to. Could it be the speed sensor on the transmission? I am stumped and dont know where else to look--fuses are fine. Is there supposed to be a constant voltage supply to the sensor? Should I try to swap the sensor out with an old one. I am not sure how they work, and the wiring in this truck seemed to be done by a shadetree mechanic. any help would be greatly appreciated!

It's probably the speed senor on the transmission. It should have 12 volts to it going in and variable voltage coming out depending on your speed. I would swap it out with another one. While you're in there clean the electrical connector to the VSS. This is maybe why it works when it wants to.

HI,
Speedometer works with the help of the sensor i think the sensor is not getting a proper supply so its better to checkout the volt :)