I have a 2007 2wd screw with the 4.6L 3.55 rear gears and 20" wheels with Pirelli Scorpion ATR P275/55R20 tires. My question is would going to 3.73 gears make much of a difference. What I want out of changing rear gears is better off the line we don't tow very often and we drive 80% freeway everyday. I don't want to impact the gass milage too much. I am installing the troyer fan kit, and I plan and getting a shift kit and programmer have a magy and intake. Any input would be great.

 

No, to see any kind of real improvement you will need to go to 4.10's.

 

Since you have a 2wd, 3.90 is also an option. But 3.73's wouldn't be worth the trouble. I doubt even 4.10's would have much of an effect on gas mileage.

 

If you were doing a LOT of towing, 4.56's would be best, the 4.6 needs to run at high RPM's to pull well. 4.10's are a good compromise for a daily driver unless you were going to go way oversize on the tires.