Ready to order - 3.55 or 3.15 diff?

[GTP]

I am ready to order my GT premium with automatic, which will be my daily driver.

This is a 12% gear ratio difference. If all the aspects of this was truly linear, then the taller ratio would imply:
50 mile longer range
$6 (2 gal) per tank savings, over and over for years.

The 3.55:1 ratio very closely matches the 3.73 Torsen diff with the MT6 box.
[Edit: Actually it closely matches the stock 3.31 diff with MT6 box.]

Do I really need to spend $400 for the occasional go-fast performance? Will I even notice it? (Note I almost ordered the turbo car, so this is already a big boost in acceleration.)

It just seems that the stock 3.15 gear helps out the already-thirsty engine.

(If this is already well discussed, please point me to the link. The term "3.55" is not very search-friendly.)

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[1st time Mustang]

3.15..or..3.55

I am ready to order my GT premium with automatic, which will be my daily driver.

This is a 12% gear ratio difference. If all the aspects of this was truly linear, then the taller ratio would imply:
50 mile longer range
$6 (2 gal) per tank savings, over and over for years.

The 3.55:1 ratio very closely matches the 3.73 Torsen diff with the MT6 box.

Do I really need to spend $400 for the occasional go-fast performance? Will I even notice it? (Note I almost ordered the turbo car, so this is already a big boost in acceleration.)

It just seems that the stock 3.15 gear helps out the already-thirsty engine.

(If this is already well discussed, please point me to the link. The term "3.55" is not very search-friendly.)

Go with a 3.55..you won't regret it.You'll love it at stop lights.You got the GT..Enjoy it like it should be DRIVEN..Good luck on your new purchase..

 

[GTP]

Thanks, and good point. I am not into the stoplight thing. But give me a clear and curved freeway on-ramp!

I really love the country road twisty bits, but I doubt how often I will get the chance to open her up out there, too.

Now ... "Opposing Counsel, would you like to cross-examine?" (Any opposing viewpoints?)

 

[bluebeastsrt]

LOL you bought a GT then talk about gas mileage. Ford offers a 4 banger for those Eco friendly types. Get the 3.55s!

 

[BULL1TT]

I have 3.55's and the car still feels sluggish in the lower rpm range. I have never driven a 3.15 geared car but I can imagine it would feel even worse. I am averaging 22-23 mpg with a mix of city/highway and get 26-27 with straight highway runs.

 

[IvanCRF]

I have 3.55's and the car still feels sluggish in the lower rpm range. I have never driven a 3.15 geared car but I can imagine it would feel even worse. I am averaging 22-23 mpg with a mix of city/highway and get 26-27 with straight highway runs.

Same here. I can idle around in second gear without having to apply any gas though. At 75mph, the car is around 2300RPM and I have yet to drive on I-10 where it is 85mph, but imagine it wouldn't be fun for the engine cruising for hours at a higher RPM. I think 3.55 is the happy medium.

 

[GTP]

26-27mpg sounds very good.

2300 @75mph with 3.55 would be 2000 with 3.15.

At the times I would be driving up to 75mph [edit: i.e. sport driving in the countryside], I wouldn't care about mpg. ;)
But I wouldn't mind better mileage for long highway drives.

 

[AMP-D]

3.55 is a great all around gear.

 

[dwaleke]

My GT PP with 3.73 felt like a dog in 6th gear on the highway (70+ mph).

I couldn't even imagine a stock 5.0 with 3.15.

Go 3.15 if you are going to put a supercharger on it. Otherwise go with the 3.55.

 

[Katastrophe]

I had the base 3.15's in my 2013 Mustang (there was no option)...they really are a great "do-it-all" set of gears. If you do any 1/4 racing, you can stick to using only 3 gears...even if you do light, bolt-on mods (sans forced induction). On the highway, it's obvious they will allow the car to just lope around with good MPG's.

On the other side of the coin, 3.55's will make the car more fun. It WILL pull harder. That = more fun.

That being said...

(These findings are with a 6750 max redline and a 265/35/20 tire)

1st: 40.3 Mph
2nd: 71.8 Mph
3rd: 110.5 Mph
4th: 147.3 Mph
5th: 193.1 Mph
6th: 243.4 Mph

That is with the 3.15 rear gear. Also, 80 Mph @ 2,200 RPM

1st: 35.7 Mph
2nd: 63.7 Mph
3rd: 98.1 Mph
4th: 130.7 Mph
5th: 171.3 Mph
6th: 216.0 Mph

This is with the 3.55 rear gear. Also, 80 Mph @ 2,500 RPM.

OP - Hopefully this confuses you even more.

For what it's worth, if 3.55's were an option back when I ordered my 2013...I would have clicked the box...

 

[OneTrickPony]

does the 3.15 include the LSD ?

I know the 3.55 has limited-slip diff.

 

[GTP]

Yes, they are all listed as LSD.

The 3.15 gives 74mph at 2000rpm. I like that.

 

[Poppacapp]

Mine is 3.15, and in no way feels slow... guess what.. the tranny downshifts!! Also, 3.15s are running as quick as 3.55s in the 1/4.

Also, 3.15 will be the PERFECT gear for my turbo setup.

 

[GTP]

Right. Here is an example for the 3.15 gear. Let's say I am going 71mph in 6th @2000rpm.

Looking at the gear chart, if I want to pass someone, I just click twice on the left paddle to go from 1900 to 3100 rpm (=71mph), then goose it to 4000rpm and I am going 90mph! Lift off the throttle and the auto shifts back up ... aaand we're back to cruising speed. Done. No muss, no fuss.

Around town? About 3-4mph difference between the two ratios for the same rpm. Who cares about performance when I am stuck behind the guy in front of me anyway?

Question - does the Coyote mind tooling around town at only 1750rpm on occasion?

 

[Remy_reign]

Go with a 3.55..you won't regret it.You'll love it at stop lights.You got the GT..Enjoy it like it should be DRIVEN..Good luck on your new purchase..

this!! im looking to swap my gears to 3.55s as soon as possible.

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