I just put 285/75r16s on my truck to replace the 255s it had on it when I bought it. I am assuming that the speedo is off now so how do I fix it or have it adjusted. If I am guessing correctly, it is just an electronic change and hopefully just a minor reprogram issue.

I would also like to change the way it shifts. If you can believe it, it seems to shift back down into drive (from overdrive) too early. If I just barely nudge it faster, it downshifts.

Thanks, I am used to the old Fords.

 

I changed tires and upgraded the gears to 4.10's. I bought a Superchips Micro-tuner. Worked great. It adjusts the computer for new gears and tire size. It adjusts the shift points. Gives you different tuning (performance options). And, it is an OBD code reader. It was worth it. Before I bought mine, I read a lot from others that bought one. No one that I have seen has been disappointed with them yet.