Does anyone know the formula for the tranny gear change required to adjust the speedometer for oversized tires? I have a 1997 F250 Light Duty so it's not controlled electronically.
Thanks all,
--Greg

 

I'm sure you'll get some answers but in the mean time, I'd suggest using one of our best features, the search function. Try typing in words like:
speedo fix, VSS gear or larger tires speedo off
I've lost track of the sites I used, but I'm sure you can find something specifically for your truck.
Mine was off 7 MPH because I went up to 285's. I know this because I had a friendly cop clock me once and much later a busy Sherriff got me on radar, who gave me a warning (62 in a 55, gawd was she bored or what!??)
Anyways, I searched the threads and went from a 20 tooth to an 18 tooth, and running against some "unoffical" readings, the speedo now appears to be within 1 mph now. Cost?
$8.00 and I did the swap in the time it took to smoke a ciggarette.
In 1999, speedo is computer controlled *if* I'm not mistaken, but you and me? A very cheap and quick fix!
Good Luck and enjoy your new home