If your speedo was already off, here's how to calculate another way. And it's probably a good idea to try this out anyways.

Head out on the highway where there are mile markers.

Drive an indicated 60MPH, which is 1 MPM (mile per minute) for exactly 2 miles.

Time the amount of time (we'll call it T) it takes to cover those 2 miles in seconds.

Your actual speed in MPM is 120/T.

So, take your existing speedo gear tooth count T/120.

Teeth(needed) = Teeth(actual) x T/120

Not a bad idea. It will have to wait till the car is out of hibernation though. Pretty soon, ... spring is finally coming! Man it's been a long winter.

Thanks for the ideas and info.

Marty

I'm with you on the hibernation thing. Maybe I'll see my Z in May.....

You're welcome!