Sorry I never explained in full...it was just a computor reset to the right ratio. The truck is a 4x4 SCrew with a 5.4. I don't believe anything is affected but the speedo and mileage. The tech wasn't sure if it came that way by accident or at sometime or other the truck was on the computor and it was switched. The truck is running great and getting much better gas mileage(or at least reading better was 14 now getting 17-19). Thanks again for all your input!