Advancing replacement speedometer to match car mileage

[Boris61]

I'm planning to replace my 84's soeedometer with a 140mph model from a 79. I'd like to advance it to the correct mileage (+ ~20k mi). Do I just hook up a drill and let it whirr until it catches up? Any advice from folks that have done this would be appreciated.

[bobplyler]

You can remove the seal (it's just wire twisted with a lead seal), and take the speedometer apart.

I did this in 1980 when my car was 1 year old and had 40000 miles. It then had 14000 miles.

[focodave]

Boris61,
I swapped the speedometer in my 1980 Spider with a 140MPH unit from a 1978 Spider.
It was very easy to reset the new odometer mileage to match the mileage on the old odometer by taking the new unit apart and following the procedure in this video (the video is for a Ford Mustang but the same method applies to the FIAT unit): https://www.youtube.com/watch?v=87kZQkKGSw8
Worked like a charm....

[Boris61]

Thanks! That should make it easy...