the difference between a 35 and 37 is negligible; so, take get them to take you to a 35, and then sit down and pencil it, once you get that initial number, actually about 6% I think off the top of my head, multiply it out, 60 will be 63.6, 70 -74.2, or just run the posted on the speedo, and know that you are slightly frying it, but not enuff to get ticketed.
miles would click away in the slow direction if it was corrected for 35, and he ran 37, or in other words, he would show 60 k, say, and have 66k actual, thereby prolonging his warranty in essence.
I am confused how changing the speedo reading helps the trans? Unless it changes shift points? that would seem to be more of a chip thing, not a speedo reprogram, educate me please.
What I have been told by the fors guys is that on the Super duties, the shift points are more based on speed and throttle input rather then rpms. Therefore bigger tires- equals different rpms and mph readings- equals different performance.
That's correct, too.
And whom did you get the chip from, it wasn't me