3.15 or 3.55 for my GT Daily Driver? 3.55 Worth the upcharge?

[ListedGuru]

Just going over my build again as I just added Active Exhaust to it. Currently I have the standard 3.15 gears on the order sheet. I will be using this as a daily driver here in Suburbia with the occasional freeway trip sprinkled in. My question is whether it's worth it to upgrade to the 3.55 gears for my use case? I've read some posts that the GT w/ 3.15 can feel sluggish around town (which I find hard to believe buy maybe)? What are the pros and cons for going with the 3.55 gears for my use case? Will I notice much better normal acceleration around town? Will my fuel economy suffer (city and or highway)?

Honestly I'm not really versed in gear ratios to not sure if it's worth the price of admission for my use case or not? I believe the MPG indicated on the window stickers for both the 3.15 and the 3.55 are both 15 city and 24 highway but I swear I saw one with a sticker for the 3.55 that said 16 city but I may be mistaken?

Also my build is for the 10A

Any advice would be greatly appreciated

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[roket]

the 3.15 will be better for daily stuff and fuel economy, but getting the 3.55 gives you more future options. ones like putting a Torsen diff (a better limited-slip diff than the standard clutch pack type) in it, changing the gears for 3.73 or 4.09 or stuff like that. the 3.55 also has better acceleration. attached is a chart i made a while ago using digital testing methods on what diff ratio is best. there's no time or fuel measurement because it's meant to be a comparison vs each other

 

[ListedGuru]

the 3.15 will be better for daily stuff and fuel economy, but getting the 3.55 gives you more future options. ones like putting a Torsen diff (a better limited-slip diff than the standard clutch pack type) in it, changing the gears for 3.73 or 4.09 or stuff like that. the 3.55 also has better acceleration. attached is a chart i made a while ago using digital testing methods on what diff ratio is best. there's no time or fuel measurement because it's meant to be a comparison vs each other

Really neat chart and thanks for posting it.

Also I found the window stickers that show the 3.55 being rated at 16 mpg city as opposed to 15 mpg which I think the 3.55 was previously rated. Not sure what changed but both of these cars are in transit so I guess both freshly built. If you can on the links below you will see an option to view the window sticker and see the city mpg rated at 16 for the 3.55

I guess it got bumped up based on more testing or data, etc? Not sure what these really means just something I noticed so I'm passing it along:

https://www.varsityford.com/new-Ann+Arbor-2024-Ford-Mustang-GT+Fastback-1FA6P8CF2R5421292

This one's a GT Convertible showing 16 MPG city with 3.55 gears:

https://www.varsityford.com/new-Ann+Arbor-2024-Ford-Mustang-GT+Premium+Convertible-1FAGP8FF8R5126925

 

[Eurasianman]

I would recommend the 3.55 with the Torsen Limited Slip. Your mileage might take a 1 MPG hit, but your acceleration will be much stronger. Since you opt for the 10A, neither will interfere with daily/city driving.

The higher the gear, you are trading increased acceleration for decreased fuel economy.

 

[HWill]

I would get the 3.55, IMO there are no benifits to getting the 3.15.

 

[ListedGuru]

I would recommend the 3.55 with the Torsen Limited Slip. Your mileage might take a 1 MPG hit, but your acceleration will be much stronger. Since you opt for the 10A, neither will interfere with daily/city driving.

The higher the gear, you are trading increased acceleration for decreased fuel economy.

It seems strange that the new GT's with the 3.55 gears are showing 16 mpg city now up from 15 mpg with the same 3.55 set up. I know you mentioned the higher the gear the lower the fuel economy but I wonder why the mpg on the sticker actually increased from 15 to 16 mpg's city and the highway stayed the same at 24 mpg. Not arguing with you just pointing out this observation.

So the 3.55 gears will provide increased acceleration around town? Is this increased acceleration something I would actually notice compared to driving at GT w/ the 3.15 gears? Also I wonder what the rpm difference is on the freeway going 75 mph. The rpm's would be higher on the 3.55's but how much higher?

 

[ListedGuru]

I would get the 3.55, IMO there are no benifits to getting the 3.15.

So I assume you have the 3.55? Did you ever drive a GT with the 3.15's? Just curious if one can actually notice the difference in acceleration between the two? I have seen people post that the GT with the 3.15's feels sluggish around town especially but honestly I have no clue so that's why I'm asking

 

[Dave2013M3]

Go with the 3.55s because if you ever want to change the ring and pinion you can't because the carrier for the 315 is different.

 

[Eurasianman]

The 15 MPG was probably for the manual. I know mine with the 3.73 gears is rated for 14 MPG in the city.

As far as acceleration, I'd recommend you test drive both and see which one you prefer more. And yes, the higher the gear, the higher the RPM when cruising. However, with the 10A, I wouldn't be too concerned about high RPMs at 75 MPH.

 

[RJV15]

I went with the 3.15 but I would go with the 3.55 if I could do it over. The MPG sucks anyways, might as well have a slightly more responsive acceleration.

 

[ListedGuru]

I went with the 3.15 but I would go with the 3.55 if I could do it over. The MPG sucks anyways, might as well have a slightly more responsive acceleration.

Have you driven a GT with the 3.55? I've been reading up more and some say it makes a noticeable difference and some seem to say they can't really tell the difference, lol. I guess it depends on the person.

 

[RJV15]

Have you driven a GT with the 3.55? I've been reading up more and some say it makes a noticeable difference and some seem to say they can't really tell the difference, lol. I guess it depends on the person.

Just my 3.15.
The 3.55 can only add acceleration, so its probably worth it regardless of how much.
The MPG aspect is a moot point IMO.

 

[93-Oct Mayne]

My 2016 came with 3.15s and always felt sluggish as all hell. I changed to 3.55s at 30k miles and it was an immediately noticeable difference in low end torque. I would never get a GT with 3.15s again. The coyote doesn't make enough low end torque as it is

 

[Dave2013M3]

I run 4.09 in my S550

 

[The Wizard]

If you want more responsive acceleration, just put it in Sport mode...

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