I went from 3.55 gears and 315/75/16 tires to 4.56 gear with the same tire. Of course this gear change did not fix the speedo so I bought a tuner. That seemed to do the trick. I recently went to Ford to have them recalibrate the speedo so I dont have to use the tuner and they couldnt do it. They said they got it close (which in reality they didnt) and they said they couldnt do it any better because the tire size is too big for their equipment or something to that nature. Does this mean I am out of luck and I have to use the tuner all the time. I dont mind using the tuner but I just wanted to see what you all think about the Ford situation.

P.S. Now my truck downshifts a little hard ever since Ford messed with the truck.

Thanks please reply with any advice or comments!!!!!!

 

From what I understand Ford can only change the factory programing to preset selections that correspond to tire size / gear ratios that were available on your truck when it was produced. So to go to a non-stock axel ratio and combine that with a non-stock tire hight I believe puts you in a position of only being able to use an aftermarket tuner to correct your speedometer/shifting issues.

good luck.

 

I think you are right. I just saw that somewhere else. Ill just reprogram the computer again with the tuner.

Thanks for your help!