1983-911SC speedometer accuracy?
 

I've checked the archives and have some idea whats going on but still not sure whats going on, my car has 7/8 inch Fuchs with 205/55 and 245/45-16 tires and the speedo seems to read high,the archives talk of guys removing the speedo,drilling an access hole and doing some adjustment,is that the only way to adjust this problem?Any suggestions would be appreciated,also is the speedo driven off the front/rear wheel or the tranny?Thanks

I have the same car and put bigger wheels and tires on it and sent the speedo to North Hollywood speedometer to be reclaibrated for those wheels/tires. cost $135, as I remember, which included routine cleaning/lubricating, and took about five days from the East Coast total.

The speedometer is driven by an electronic sensor on the right side of the transmission/differential housing. It picks up pulses from magnets--I believe four of 'em--mounted on the differential ring gear, I believe, as they spin past it.

Stephan

There is a pot on the speedo that can be adjusted. I also sent mine to N. Hollywood speedo for calibrating.

As I recall, and someone correct me if I'm wrong, even if the speedo itself is callibrated, the odometer callibaration does not change. I think someone from NH Speedo told me this at this year's German Auto Fest.

Does this sound correct?

That is correct

I adjusted the internal pot and the odo didn't change