Ready to order - 3.55 or 3.15 diff?

[Rich of So Cal]

3.55 all the way. I have driven both and it is worth it if you actually will go fast or if you ever plan to go to the drag strip. If you are gonna drive it like a grandma it wont make a difference.

lol. there's a lot to choose from between 'track' and 'gma'

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[Turrizm]

3.55 is a great all around gear.

I agree. No brainer. Get the 3:55 gears

 

[bluebeastsrt]

My 3.15 equipped Gt is not sluggish at all. I believe the track times these cars are turning in states that too.

Im sure the 3.15 cars are doing fine but I'd bet the steeper gear is worth a 10th or two more in the 1/4 mile in an otherwise stock GT

I'm sure you can tell a difference if you drive it long enough, but I did a test drive with the 3.55, then the car I bought came with the 3.15. With an automatic I couldn't notice much difference. But then, my time with 3.55 was limited. If it hadn't been black, I might have bought the test car....but I am getting out of an 8 year relationship with a black car, so no thanks. Maybe I'll upgrade later, but having lots of fun with what I've got, even at stop lights!

Nobody will feel a 10th in the zero to sixty or two tenths in the 1/4. You'd actually have to run your car at the drag strip and see the difference on a time slip.

 

[Cascadia_302]

Im sure the 3.15 cars are doing fine but I'd bet the steeper gear is worth a 10th or two more in the 1/4 mile in an otherwise stock GT

Nobody will feel a 10th in the zero to sixty or two tenths in the 1/4. You'd actually have to run your car at the drag strip and see the difference on a time slip.

This^ but even more so running DR's or slicks. This is where the 3.55's will shine over the 3.15's.

Edit: To the OP...as for a DD don't even worry about it, save (gas) money and your money by keeping the 3.15's.

 

[GTP]

After further gear-chart research, it would seem this is a 5-speed car, with a 6th highway gear. The MT6/3.73 or AT6/3.55 reach wind-drag-limited top speed of ~160mph when at/near redline in 5th gear. Gearing taller would likely hurt top speed. But I don't intend to reach top speed.

My Challenger SRT friend decided to simulate the 6th gear, 3.55-ratio situation last weekend.
He said this: "Just drove to a huge cruise-in. Used 5th on the highway for 20-30min. 2300 at 70. Annoying. I felt like I kept needing to shift up. Get the 3.15."

In conclusion, since I won't drag race on a strip or from a stoplight, but might gas it up the on-ramp (70mph in 2nd gear!), or drive spirited in the countryside ... I decided to stick with the stock 3.15 ratio.

Furthermore, after watching videos of Mustang's spinning out with relative ease, I think it is important for me to practice rolling on and off the throttle smoothly. ;)

I REALLY appreciate everyone's weigh-in on this topic. It was helpful to hear both sides of the debate.
:cheers:

PS> I would like to say that an even more important decision for me was to get the automatic over the manual. I, personally, really loved the way it upshifted and rev-matched downshifted. And moving the gear shift between D and S really simplifies the modes. I will probably only use the paddle to downshift when I pull out to pass.
I will post later how I plan to DIY my own Performance Package.

 

[GoBlues38]

My Challenger SRT friend decided to simulate the 6th gear, 3.55-ratio situation last weekend.
He said this: "Just drove to a huge cruise-in. Used 5th on the highway for 20-30min. 2300 at 70. Annoying. I felt like I kept needing to shift up. Get the 3.15."

.

This is one of the worst apples to bananas comparisons ever.

 

[GTP]

This is one of the worst apples to bananas comparisons ever.

I was trying to illustrate that his 5th gear is the same as the Mustang's 6th gear, with the 3.55 diff. Both cars turn 2300 at 70mph, and it got on his nerves after a while.

BTW, he also was recommending that I get the 3.55 diff at first, until we discussed it much further. Note that his 6th is 0.5:1, very tall, and so that may be why he "couldn't relate" in the beginning of our discussion, which was held over a couple of days.

I realize my choice focuses more on 6th gear at highway speeds at the expense of performance <60mph. But again, I care more about braking, turn-in, apex, and throttle roll-on, than I do about straightline times. My first upgrade (next year) will be summer wheels, followed by suspension.

Don't forget - I decided to switch up from the EcoBoost just two weeks ago!

 

[Spartan]

I'm kinda curious why the EB premiums get a 3.31 gear in the Auto but the GT premium Auto is at a 3.15 unless you get the 3.55 or PP?

 

[comagt]

If you're going to stick with stock HP and don't do a lot of highway driving then the 3.55 would be appealing. However, if you're ever going to add boost down the road the 3.15s will serve you better long term. I went with the 3.15s and there is no shortage of power with the 6R80 gearing up front.

 

[MikeD1]

Can someone chime in on why the 3.15's are a better choice if supercharging vs. the 3.55's ?

I have a 3.55 car on order with plans to put on the Roush s/c @ delivery. Both the dealer performance guys & the Roush folks seemed to think I would be happier with the 3.55 set-up. Don't plan on doing any drag racing & the car is not going to be a DD.

Did I make a mistake listening to these guys ?? Should I try to change the order & drop the 3.55's ?

 

[Poppacapp]

Can someone chime in on why the 3.15's are a better choice if supercharging vs. the 3.55's ?

I have a 3.55 car on order with plans to put on the Roush s/c @ delivery. Both the dealer performance guys & the Roush folks seemed to think I would be happier with the 3.55 set-up. Don't plan on doing any drag racing & the car is not going to be a DD.

Did I make a mistake listening to these guys ?? Should I try to change the order & drop the 3.55's ?

If you never plan to go to a track, 3.55 and enjoy. depending on your et/speed, the 3.15 vs 3.55 could save a gear change at the end, meaning quicker time. I went with 3.15s in mine because it is the perfect turbo/twin turbo gear.

 

[SK GT]

I love my car with 3.55s.

It's a street car that won't see the 1/4 mile for me at least.

 

[Five Oh Brian]

Can someone chime in on why the 3.15's are a better choice if supercharging vs. the 3.55's ?

I have a 3.55 car on order with plans to put on the Roush s/c @ delivery.

Gears are - by definition - a torque multiplier. A Roush S/C makes a ton of torque already, so "most" people generally do not need additional gearing to generate torque and should stick with the 3.15's.

Now, if you were going to stay naturally aspirated, or went with a centrifugal supercharging instead, you'd have very little torque down low (compared to a positive displacement blower like the Roush S/C), so you'd want the extra torque multiplication that steeper rear end gears offer (i.e. 3.55's, 3.73's, 4.10's, etc.).

I think you're okay with the 3.55's and the Roush S/C, though. I'm a gear junky and really like lots of gear. I have 4.10's in my '14 GT automatic. Had 4.56's in my '11 GT manual. Had 4.10s' in my Vortech supercharged '07 GT automatic. Had 4.30's in my '03 Mach 1 manual. et cetera. Torque multiplication is fun! And, with a modern overdrive transmission, the fuel economy hit isn't much at all.

 

[bluebeastsrt]

I personally think a performance car will benefit from a performance gear ratio 99 times out of 100. 3.55 is what I choose for my automatic.

 

[Krilla5.0]

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.

For real. I’m about to put 4.10s. The low gears it current has in the 3.15 take forever to go through

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