My speedometer needle “bounces”

Question:

The speedometer needle bounces all over the dial when it hits 50 miles per hour and over, but until 50 it works fine. It has been rebuilt and the cable is fine. I’ve replaced the drive gear on the transmission a couple of times. Any ideas?

Answer:

You have already checked every component of the speedometer and its drive, so it is hard to diagnose what might be wrong from here, but since the gear is working properly up to 50 miles per hour I would guess that it is not the problem. The cable drive could be malfunctioning, but it has been my experience that when that occurs the reading will go rhythmically back and forth and will be constant, though increasing as you speed up. Also, the cable will usually make a rhythmically grinding noise in concert with the bouncing of the needle. Therefore, I would have to guess that the gauge itself was not rebuilt properly or that the little gears in the gauge itself are misaligned, defective or possibly not properly lubricated.