My speedometer on my 84 f 150 w/ cruise was jumpin and actin up so I pulled it apart and greased the cable and then put it back together. Aint nothin changed...still jumps and is about 30 mph slow. The gear is fine. I'm wonderin if it's in the cruise counter thing or if its in the speedometer itself. Can anybody tell me what all's in the speedometer part itself and any possible fixes? Appreciate it.

 

Similar problem with the speedo jumping and cruise control installed. I found that one end of the speedo cable was not fully engaged in the speedometer. I also double checked the other ends to make sure it was engaged at allpoints. It fixed the problem and could be the cause of yours.

-Kerry

 

I have the same problem with my '84. The gear on the output shaft is worn enough that it won't drive the cable gear (new). I am trying to get ambition to pull the tail housing off and fix it.