Erratice Speedometer

I have a 85 S10 with an erratic speedometer. Once it hits 45 mph it starts bounceing all over. I took the cable out, cleaned and lubed it. I also put a drill to the speedometer and did not get any jumping. Any suggestions?

Take a close look at the gears where it goes into transmission.
Check both of the gears or the housing for wear.
MT