My 86' Monte SS has recently been overhauled with all the new additions, but one small problem that is puzzling me and even my mechanic was one with the speedometer. With the new motor we aquired a device that tracks my speed through this box where the wire spins through the transmission to show speed. This way I could use the original speedometer. However the problem is when speeds are around 5-20mph the speedometer needle wobbles wildly between 0-35mph UNTIL I reach about 20mph then the needle catches and begins recording the correct speed. My mechanic couldn't figure it out and neither could I. So I wanted to ask around to see if anyone has any clue as to what's happening. The box that records the speed was about 500 bucks and I want this to work properly. Any Ideas?

Forrest

 

my 78 did this also. you need to change out the speedo head in the dash of the car. this is not hard to do just take the time to make the miles correct if ya need to.

if it is not this it is the plastic pin that gose in to the back of the speedo head and or the tranny. this is the gear for those years and it will some times round out in there and couse this also.

to replace it is not that hard just might be tuff to find the same speedo head any more so you might have to get creative and change the face from yours to a nother one belive in that year they were still held on with the two screws on the face. just take the needel off real careful like and then unscrew the face and replace it then revers.
when taking the needel off mark it and what i used to do was mark both ends of it on the back of the speedo head so it was correc again and would with luck be real close fo ryour speed again when done