Your Tire Size (TS) is way too large! I'm surprised it's only 4 mph off. A larger circumference makes the PCM think you are moving faster than you really are.

Bill has this neat "Gear Ratio Calculator" in Pegasus that I use for TS. All you have to do is put "315/70-17" (notice the dash in front of 17) into the Old Tire Size box. You will immediately see 2672 mm in the Old Circumference box. Notice the "Squish" bax has a "5" in it. The circumference is being adjusted for a 5% "rubber squish" (what Ford uses). I get better results with 7%, so if you change the "5" to "7", you'll see 2644 mm.

Try either of these values, and adjust as necessary.

- Jack

Jack, I am retarded :doh: I guess Bill set it up for me and when i went to change the tire size it was 2673 and what do you know? it is spot on :smiley_roll1: Thank you for the help!:2thumbs:

Not at all my friend! I'm glad you got it figured out.

- Jack