It takes some playing around to get the pinion factor set not using the factory tire size. This is not something a tech can look up in a book, or call tech for as it's an emisions violation to change that data. I can do it quick now that I know what I'm doing, but the first couple took some playing around. I've also found the rev per mile number sometimes doesn't give you the results you want. I use a GPS and make adjustments on the road until it's on.

 

I just had the calibration done today, the truck does seem to shift better w/o as much hunting. The tire size is 35x12.5x17, and my revs per mile is 598.

 

i also talked to jmac and he said it did on his too whe he put his 315's on iguess i was wrong, used to the old noncomputerized ones sorry