I have searched the site hear and have found all sorts of varying possibilities for what might be controlling my speedometer for varying years, but can't seem to find a specific post for my year.

I have a 97 F250 HD Powerstroke with the 5 speed manual and stock 4.11 limited slip rear. I am planning on changing the rears to a 3.55.

Does anyone know how this will affect the speedomter and/or anything else electronic? And how I would correct? I have gotten different answers from different Ford dealers I have called.

Thanks.

 

The speedo is controlled through the PCM via the VSS in the rear-end. The VSS takes a reading off of the ring gear and converts it to speed. Since the ring gear travels at the same rpm as the tires, I don't think that you will need to recalibrate anything. Keep me posted, I'm considering doing a gear swap on my truck as well. Thinking about a 3.73 locker.

Max

 

Thanks,

I'll Take a look at it this week sometime.