I would try lubricating the speedometer drive cable, before you send the instrument in for repair .
The method I use, is to cut the corner out of a stout plastic bag, remove the drive cable from the indicator, remove the other end of the cable from the transmission .
Stick the trans end of the cable through a plastic bag, then chuck the trans end of the cable into a cordless drill, or something similar .
Take the plastic bag at the indicator end, put a ty-wrap around it on the drive cable sheath, try to get as fluid tight a seal as you can .
Place alcohol into the bag at the top, hold the plastic bag at the drill end, so it doesn't rotate, and get the liquid all over, then turn the drill motor on doesn't need to be a fast speed, the alcohol should flow down the cable, repeat, until you are satisfied it's clean .
To lube it, place a light oil in the plastic bag at the top, and do the same routine .
Be sure you have a drip pan to catch the dirty alcohol, and oil, as it exits the lower end .
I've been doing this for about 12 years, since I learned aboput it from a speedometer repair shop, that repaired the inoperative odometer on my speedometer .
