I'm sure this question has been asked many times over, but the circumstances can always vary.
VEHICLE: Bone stock '05 Mustang GT - Automatic.
PLANNED MODS: CAI, tune, gear
I have the CAI and tune issue figured out. I am going back & forth between 3.73 and 4.10 gear set(s). I'm thinking a 3.73 may not be noticeable and a 4.10 may be too much.
I'd like to hear from some owners with automatic GTs who have made the change and let me know of your "pros and cons".
My GT is driven 70% city with the balance of expressway at speeds no greater than 75-80 MPH. Fuel economy would be a factor if out of control but I don't think there is that great of a difference.
My first thought is that a 4.10 would be a little to "tall" for an automatic car and I would experience a lot of "shift busyness", but I'd like to know of both the upside and downside of both gear sets from those who did the change and their own experiences.
Thanks

 

A lot of guys on here have the 4.10's with the auto and love them. There are also quite a few with the 3.73's as well. There are 3.90 gears out there if you want to try those out. If your car is mostly driven in the cities then I would just go ahead with the 4.10's. I'm sure you will love them. Good luck with the decision!

 

I would just do the intake and tune first and see how you feel after that. To me, the intake and tune made a huge difference and the switch from 3.31s to 3.73s was barely noticeable. Also, just so you know, 4.10s are a "shorter" gear than 3.55s, because you cant go as fast in the same transmission gear with 4.10 rear gears.

 

To the OP just try the search function. You will find a TON of threads about auto's with 4.10's and 3.73's. That will help you out a lot with your decision. Good luck!