The rear end in my Expedition has started making some noise, so I may be looking at replacing the gears before long. If I do, I will probably go ahead and regear to 4.10s. I am currently running 33s, with an eye toward 34s at next tire change, if I do a lift. My question is for anyone who regeard ffrom 3.55s to 4.10s. What did it do to your gas mileage? I would expect a slight decrease on the highway, but a slight improvement around town.

 

You may see a very slight improvement on the highway, because it will stay in overdrive with the TC locked up a lot more. However, the larger tires and the lift will hurt the mileage no matter what you do.

 

ive got 32" tires on my 4.6 and just recently did 4.10s. My gas mileage improved pretty much all around. Not a huge improvement, but noticeable.