1981 speedometer new face calibration change
 

So if one buys the new 140 mph face from Corvette Central, what else must change to make it work correctly at all speeds? New gear in the trans? I searched and found a service that does it, but what is it they do?

Thanks

I bought an early '79 speedo and tach from a forum member. Now I have a 140 mph speedo and the L-82 tach in my (originally L-48) '80. Seems to be accurate compared to road traffic after driving for several miles so I'm happy. It's a bunch cheaper than the conversion services from my experience. Just saying'...

Good call, I will try that and see what I get for reply

I've redone speedo faces on 85 mph jobs, when there were more calibration places around. If you look at the inner workings of a speedometer, there's a round magnet spinning inside a metal cup, held back with a clock spring. Speedo shops, change magnet and clock spring strength. You're not wanting to change drive gearing, or the odometer will be way off. Haven't done this in a awhile, but "speedometerrepairguy.com", could surely help out.