A10 3:15 vs 3:55

Hey Guys/Gals new to the forum.

I searched before here and google to any insight but I didn't find any creditable information.

I am going to be in the market for either an '18 or ordering a '19 very soon, and with either model year it'll be with the A10. I'm looking at both the 301A package in the GT, or just getting the premium, so no matter which I chose both would be equipped with the driving modes. Now I'm not looking at the PP, the brembo's and strut tower brace aren't a big deal to me, as the car will be a daily, and never will be on a circuit track, and maybe a drag strip twice a year.

With that said, with the 10 speed and its gearing so close together do you guys feel that in stock or lightly modded form (Intake, Tune) that the 3:55 has a big advantage over the 3:15, or would it be minimal with so many gears? There are quite a few cars in my selling area with 3:15's, but a smaller amount that are non PP with the 3:55 option. So what would you guys say would be the difference in the 1/4 between the two gear sets in drag mode?

Thanks guys

I had the same thoughts when buying mine. It seems the 355 gears will have a slight advantage in performance and also the housing they come in allows swapping gears without swapping the whole rear. The 315 however is slightly better for fuel economy and many cars with it have gone fast at the track as well. For me I saved the money and went with the 315 as mid to low 11's will make me happy at the track and I daily mine 40 miles each way. I sometimes think about whether I made the right decision but in the end the swap to a different gear wouldn't be too hard with swapping the whole rear and honestly the difference in performance with this many gears is pretty small. I doubt in a side by side race it would amount to more then a fender. I would probably go with the 409 if and when I stop driving mine every day and want the most for the track.

As a follow up question, if you don’t get PP1 or PP2, but custom order the 3:55, is it the same 3:55 you would get with either PP? It is confusing to me. Do all Mustangs have a positraction or just the PPs?

If I had to do it again, I'd go with 3.55. I feel like the RPM are too low in tenth gear when doing 40-45 mph in D mode - it feels sluggish in that situation, and can lug when trying to accelerate. Yes, you could manually upshift, or just use S mode, but I don't want to HAVE to do anything. It seems like those with 3.55 don't notice the issue as much if at all since RPMs are a bit higher. See this thread: https://www.mustang6g.com/forums/showthread.php?t=102341

the PP has it for some reason id guess? and fords performance figures are based on the PP with drag mode. but personally i say 3:55

Dory said:

As a follow up question, if you don’t get PP1 or PP2, but custom order the 3:55, is it the same 3:55 you would get with either PP? It is confusing to me. Do all Mustangs have a positraction or just the PPs?

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Yes if you order a '19, or purchase a '18 that is a NON-PP, but it has the 3:55 gears option, it gets the same limited slip as the PP. But no matter if you get the 3:15's it has a limited slip as well from the factory.

Dory said:

As a follow up question, if you don’t get PP1 or PP2, but custom order the 3:55, is it the same 3:55 you would get with either PP? It is confusing to me. Do all Mustangs have a positraction or just the PPs?

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They both have posi but the PP gets a Torsen diff. I'm not sure if the factory option for non PP cars is also or not. If you are racing around a track then the Torsen diff is supposed to be better. I have found it to be more noisy and feel a bit funky around slow speed tight turns (making a turn out of a parking lot slowly). At least this was my experience with my 15 PP. I have none of that with my base 18. I can also still lay down an awesome set of 11's if I want. If you daily the car and don't track race then pick whats right for you. Like I said I still waffle a bit on if I would pick the 355's if I had to do it again. At the time the car had just come out and I remembered that the 6r80 guys did best with the 331's and worse with the 373's and 410's in some cases.

my belief after driving both. mid to low HP. the 3:55 will feel better daily driving.. more "peppy" if going to make a big boy drag car it probably wont matter much but might lean to 3:15

bluebeastsrt said:

With a computer controlled 10 speed. Does a slight difference in gearing really make any difference anymore?

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I was pondering the same thing. :shrug:


Anyone want to compute/put up a gear ration vs rpm vs mph graph, for each A10 ratio...?

I would like to compare (visually) the gear overlaps, etc.

bluebeastsrt said:

With a computer controlled 10 speed. Does a slight difference in gearing really make any difference anymore?

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Good point, I'm glad I got the 3.55's since I also have the 20's.

right i hear with the steeper gears you get a 28inch tall tire and with the base gears you get a 26 inch tall tire or change based on power

Wish I had gotten the 3.55, I’ll be upgrading. That said the 3.15 is darned fast. The pp cars get the Torsen diff, the 3.55 in the non pp cars is not the same. It’s a less expensive diff. No clue how much if any better the torsen diff is. If you plan on adding a blower or turbos stay with the 3.15

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OP, I have 3.55 with my A10 and I would not go with anything lower. Personal opinion.

I feel the car is peppier and willing to downshift compared to 3.15. When I test drove the 3.15 rear end 2018 GT and then a 3.55 rear end, I knew right away what I wanted. The car feels a bit more alive even when in 10th gear when comparing to 3.15. I doubt you will have a significant change in MPG from 3.15 to 3.55. The car is doing 72MPH at 2000 RPM in 10th gear. Cant ask for anything more from a performance car