Currently I'm running the stock 3.42's and I'm trying to decide between 3.90's or 4.10's. When I regear I will have 255/45/20 tires (29.1"). I basically want to get the truck more in it's sweet spot so I figured gears should be #1. So, should I go with 3.90's or 4.10's? What should I expect in gas mileage suffering? Any help/comments would be great

 

I didn't no they made 3.90's, but I would vote for the 4.10's. Gas mileage will obviously suffer some although I would suspect mostly with highway driving. I don't think you will see much difference with city driving mpg.