I am running the 4.10s and with all the other mods including the stall converter I could still average 24 mpg on the highway if I could manage to stay out of it, so I dropped about 2 mpg when going to the 4.10s. pulls a lot harder out of the hole, but then traction becomes an issue if you have many mods. I like fordfanboy will probably be switching to 3.90 gears soon because more mods are to come in the near future.

 

I went with 3.73's and Im pleased by the results. It makes quite a bit of difference. It will put a smile on your face.

 

I have 3.73’s and am very happy with my choice, unless you want an all out ¼ mile car I would go for the 3.73’s. You can get a feel for what 4.10 gears would be like at cruise with your auto by taking the overdrive off, this is about the same rpm condition you will have with 4.10’s. With 3.73’s I turn 2500 at 75 mph with a 27 inch tire which is a pleasant cruising rpm.

Earl