Hat should I expect swapping 4:10 gears into my automatic mustang? Should I do 4:10 or 3:73. I think 4:10 but just wondering. What should I expect on mpg and RPMs coming from stock.

 

What year/model is your SN95 Mustang?

 

Evil_Capri it is a 2000 GT

 

If you do much driving on the highway you won't like 4.10's. You would be looking at less than 20mpg on the highway and lots of noise. I would probably go with 3.73's. Before the Supercharger my car was lightly modded and I ran 13.8x on street tires and got 27mpg highway/23 city. With 3.73's you should get 20+.

 

And here is a quick chart of Gears/RPMs/different transmissions . . . (you have a 4R70W, in case you didn't know.)

http://www.americanmuscle.com/mustan...rpm-chart.html