trying to program the gear ratio and tire size on my 06 f150 4wd with 37x13.50 tires and 22x12 wheels so i can get my speedo back on track as well as my shift points.

on my edge it has the stock gearing on there which is 3.73.

Wouldnt i need to input my final drive ratio that the tires decreased the gearing down to, into the programmer? i used a calculator and it says since ive added the tires my effective gear ratio is now 3.23. should i input 3.23 for my gear ratio, and then input the 37" tire size into the programmer?

i have tried leaving the 3.73 on there and input my 37" circumference for the tire, which i was guessing was the correct way to do it and the speedo is off by like 10mph compared to my gps. can someone enlighten me here?

 

Use trial and error till the speedo is about 2 mph faster than the GPS at 60 mph.

 

You use the actual ratio, 3.73. When you enter the number for your tires, it calculates by using a formula.

 

Yes, and you need to put in the tire circumference measured in millimeters, less about 3% for squish.

Your tires are 2951 mm.

 

thanks for the reply guys. so 2873 would be the value after deducting for the squish?

 

Yes and after you get it programmed, see how close it is to a gps.