clingbat

I know there are a lot of gear posts, but I could not find much input specifically on the 2011+ V6 automatic gear swaps. Most convos refer to manuals, which may be a slightly different story.

I have 2.73 stock, and even with tune/cai it's a bit sluggish off the line so I'd like to upgrade. Was thinking 3.55, but saw a few mention the 3.73 might be better for automatics. If 3.31 does the job just fine, that'd be an option too though I'm not sure the 3.31 is worth the price w/ labor. Wish I had gotten the 3.31 from the start, but the car was already on the lot and I loved everything else about it.

Looking for the ratio that gives me a bit more bite down low, but doesn't murder highway mileage and/or rev high enough that my AIRAID cai becomes obnoxious during cruising (~2500rpm).

Any advice/experience would be greatly appreciated, and please keep in mind I'm looking for info pertaining to 2011+ V6 automatics only. Thanks!

schram1

I went from 2.73 to 3.73 but it killed my gas a lot quicker tho

audioAl

3.55:1 is what I am going to. You will have to make this choice on your own.

kzonts

I'd say 3:55 is a good choice to keep your highway noise levels and RPM's down, but there's not much difference between that and 3.73's. You certainly don't want 3:31's.

hogasswild

Each gearset has its advantages/disadvantages:
2.73-fuel economy
3.31/3.55-improved performance with reduction in fuel economy
3.73/4.10-performance

Now with that said, I went from 3.31 gears, which were nice to start with. They give you a little snappier off the line performance without killing MPGs. After the switch to 3.73s, my highway MPGs dropped from30.5 to just over 28mpg. However I also got bigger tires and wheels so about 0.5mpg of that is due to the wheels. My combined driving is still about 24mpg which is the same as my stock 3.31s. Obviously, everyone drives differently so YMMV. I just got a DS so I'm measuring to see if I got any of those MPGs back. I would say if you do a lot of highway driving you might want to stick with 3.31s, but I also wholeheartedly recommend 3.73s. I feel the mpg difference is negligible. I own a manual v6, so didn't want to pipe in, but the MPGs differences are 0.

mustangergt

I had a 2011 V6 auto. I got 31 to 33 on highway. Combined 26 plus.
But I did not buy it for mpg. I wanted a Mustang and at the time the V6 was in my budget. So I got a CAI and tune from Bama, put BBK long tub headers, X pipe, magnaflow, and 3:73 gears. I also had the dealer I bought it from do all the work.
Result was one fast V6. I had had an older V8, stock, and this was quicker off line.
However the price to play, which to me was worth it, was lower hwy mpg. About
24 , doing 75. Would not have changed a thing.

THS_Steed06

I'd say you have to decide what's more important. Do you want the best acceleration you can get or do you want to retain some good mileage? Yes to both is probably the answer

I have 3.31s in my car with the T-5 manual and they are great. Good off the line and the 4L is running less than 2k at 55 MPH. I can still pull 25-28 MPG on my 40 mile daily commute (70% highway) and I don't really baby it and skip shift.

My 2010 GT had the 3.73's with the TR3650 5 speed, and while that car was a blast to drive on the same commute struggled to get above 22. I know you can't compare 4L to 4.6L fuel economy but the engines only have 30 cubic inch difference and the GT weighed about 300 lbs more. My 4.6 was running above 2k at 55 MPH so the swing is probably about 300 to 500 RPMs from 3.31 to 3.73.

I think since the 3.7 is already not thirsty you can get away with 3.55's and not suffer much but the 3.73 will definitely eat more at the pump. Whatever you decide to do I would definitely reccomend you get the t-lock along with your gear....you'll feel it and put the power down better. I'm planning to upgrade mine to 3.73 t-lock and get a ne DS from shaftmasters to firm things up really nice.

Tom

clingbat

Thanks everyone for the responses. I'm leaning towards the 3.55 at this point but still open to any opinions. My only hesitation with the 3.73 was really highway sound as opposed to mpgs, as my wife and i take the stang on long highway trips and she's not a big fan of noisy. I calculated the rpms at 80mph (my usual highway cruising speed) from the AM rpm charts for 3.55 vs. 3.73 you get 2420 vs 2543. Then i went out and put it in 2nd and drove down a road using the engineering diag rpm display to get steady right around those rpm and 2400 sounded a bit lower/calmer than 2550 which is nice. It wasn't an earth shattering difference, but it's amazing that 100-150 rpm does actually make a noticeable difference. From the comments about mpgs w/ the 3.55, that's def a plus since it's my semi-DD - i work from home so how much of a DD can it really be

schram1

3.73 if you want to go fast and dont care about mpg

mpd3244

I ran my 3.7 for the first time this weekend and was able to muster a 13.999 at 100.37 mph with a few bolt-on's. I too plan on getting the 273 gear out and going to a 355 or 373, which will easily make that time change.