Here is the test I performed today. Drove 100 miles, mostly interstate today on a trip. I used this opportunity to check over a long distance. I started at a mile marker and zero'd the car odometer, and GPS at same time at that mile marker. At the 100th mile marker, the GPS registered about 101, the car 110. At 80mph GPS, the car speedo was reading 90mph. So basically, when the car trips 36,000 miles for the warranty, the car will only have been driven 32,400. Is this enough to worry about? I can live with a 5mph difference between 65-70, but 10mph at 75-80 is a bit much when trying to gauge your speed on the highway.

 

Yes I'm having them and today when I took it to the Ford Dealership it quit. Generally after it has been sitting in the sun all day it starts showing the speed less than actual speed. They can't see me Saturday so I'm going Monday. A course I receive the computer anxiety treatment. I know that chip doesn't have $hit to do with it. But he said he doesn't know if the warranty will be honored because of the computer being change. Like Fu@k me running. I hate feeling guilty for this stuff. I've also had my gears changed to 4:10 and I know that the SCT Tuner has done it's job and the ford place is just trying to make me squeal. Anyone with advise?

 

Buy a tuner. Whatever gear ratio you have, tell the computer you have one step lower gears. If your gears are 4.10s then tell your computer you have 4.30. Your speedo will be off the same amount, but in the other way.