When I first got tuned, my tune had values for having 4.10 gears in the rear end and the factory tire size. The rpo codes in my glovebox, show that I have 3.73's. I've been the only owner of the truck and have not swapped to 4.10's. I corrected this in the tune with the proper gears and tire size and have never been able to get the speedo accurate with the 3.73 ratio. I put it back to 4.10's and now it's dead on...... Why is this? The rpm still reads like I have 3.73's when cruising. I like the fact that my speedo is accurate now but curious to why my truck's tune was like this from the factory. I've tuned an identical 3.7L regular cab and it was also like this.