CaptainRon

I have a 2012 Mustang V6 M6 with the 2:73 axle. I've been thinking about changing the gears out with a set of 3:55 from American Muscle. basically I would like some extra zip without killing my gas mileage too much. Also if we change out gear ratios, do we have to recalibrate the speedo?

hogasswild

I am getting 28 highway mpg with 3.73 gears if I can keep it below 75mph. Any gear change you make will be a big improvement over the 2.73s, but I recommend 3.73s. My car originally came with 3.31 gears, so I wanted to know I was making a difference over what I already had. 3.55s weren't really something I considered. I think 4.10s are too deep for most people and basically eliminates the need for 1st gear.

You will need to get a tuner to recalibrate the speedo. The faster you drive the more your speedometer will be off. Don't forget that it will also mess up your odometer as well if you don't get it recalibrated.

Funster_2011V6

All of the 2.97 cars I test drove felt sluggish to me. No cars were available in my area with 3.31 however so I special ordered my car and got other things exactly as I wanted as well.

For a dd or cruiser 2.97 would be fine, but for sportiness I like my 3.31s.

CaptainRon

Sorry for the noob question guys but is doing a gear swap and recalibration something my dealership can do? Or would you guys suggest staying from dealerships for these types of work? I say this because i have only 1700 miles on my car, and I would think that the dealer mechanic know what they're doing and done this before....

hogasswild

2.97?

hogasswild

Your easiest and probably least expensive route is to buy a tuner for the car. You can then change the gear ratio from there. Some shops will recalibrate for you as a part of the gear swap, but they are using a tuner as well and then you can't make any other changes later on if you want. You can get a tuner from Bama/American Muscle with lifetime tunes for under $360 with forum discount:
http://www.americanmuscle.com/x3-cus...er-2011v6.html

Funster_2011V6

2.73 my bad.

Funster_2011V6

It's been confirmed that dealers simply don't have the software to calibrate the spedo to any ratio other than what the car came off the assembly line with so it just doesn't make sense to use them at all for this type of mod. Use a reputable tranny or speed shop instead.

So just think of the tuner as part of the cost of the swap. But then you still have it for more mods down the road.

jdmcbride

Just remember, the 31 MPG highway rating on the sticker is always for the base gear ratio (the 2.73 in the case of the new V6). The lower you gear your car the more you will decrease your MPGs.

So if you bought your V6 for the high MPGs, you might want to look at other mods that will increase rwhp while increasing/sustaining MPGs - like an aluminum driveshaft, lighter wheels, or underdrive pulleys(not sure if they make this mod for the 3.7l or not).

hogasswild

Intake, octane and tune each modestly increase mpgs. All together you can see a couple extra mpgs. Some would argue whether it's worth it to run 93 octane or not due to the efficiency improvement not being high enough to justify the cost.