3.15 gear?

[Gdyup50]

Hi, I know nothing about gearing or gear ratios, but I have noticed that I have seen everyone talking about 3.31 and 3.55 gears, I noticed on my sticker that I have 3.15, can someone explain to me what that means, and why nobody else seems to be talking about that ratio? Thanks

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[DR_]

It is the tallest (numerically lowest) of the gears available and comes standard on all three engines on the automatics and well as on the V6 manual. It should give the best gas mileage of the available options (lowest RPM for a given speed) but also the worst acceleration (least mechanical advantage). In contrast if you would have gotten the Performance Pack you would get the 3.73 differential which is the opposite and gets the worst mileage but best acceleration.
One nice thing is that with your automatic you also got the aluminum differential carrier which is lighter than the cast iron carrier that the manual transmission cars come with.

 

[Gdyup50]

So basically I am slower than everyone else? LOL

It is the tallest (numerically lowest) of the gears available and comes standard on all three engines on the automatics and well as on the V6 manual. It should give the best gas mileage of the available options (lowest RPM for a given speed) but also the worst acceleration (least mechanical advantage). In contrast if you would have gotten the Performance Pack you would get the 3.73 differential which is the opposite and gets the worst mileage but best acceleration.
One nice thing is that with your automatic you also got the aluminum differential carrier which is lighter than the cast iron carrier that the manual transmission cars come with.

 

[DR_]

So basically I am slower than everyone else? LOL

you could whoop my V6 :cheers:

 

[Gdyup50]

Wow I'm so happy about that...So what would it cost me to switch gears??

you could whoop my V6 :cheers:

 

[DR_]

There are a couple ways to do it. One is the buy the gears and install kit (< $300) and pay a lot of labor to have it installed. You then have a very high chance of gear whine. The other way, and IMO the smarter option, is to find a complete pumpkin out of a wrecked 2015 Mustang ($500-$700) that has the gear ratio you want and have that swapped over. That will cost more for the parts but much less for labor and much less chance of gear whine.

 

[Gdyup50]

Will be less for labor because it won't have to be opened up?

There are a couple ways to do it. One is the buy the gears and install kit (< $300) and pay a lot of labor to have it installed. You then have a very high chance of gear whine. The other way, and IMO the smarter option, is to find a complete pumpkin out of a wrecked 2015 Mustang ($500-$700) that has the gear ratio you want and have that swapped over. That will cost more for the parts but much less for labor and much less chance of gear whine.

 

[DR_]

Will be less for labor because it won't have to be opened up?

correct. I would guess twice as much for labor to open it up. So hypothetically 2 hours to just swap the pumpkin but 2 additional hours if they are opening it up and installing the gears.

 

[Gdyup50]

OK, and why would I get gear whine if I put a new one into my car?

correct. I would guess twice as much for labor to open it up. So hypothetically 2 hours to just swap the pumpkin but 2 additional hours if they are opening it up and installing the gears.

 

[DR_]

Getting the pinion preload and the carrier backlash (controls how the gears mesh together) is tricky. I have had problems with this in prior cars. This time I hope to find the holy grail (3.73 w/torsen) pumpkin and swap the whole thing over.

 

[Gdyup50]

OK well thanks for your help, at least I know a little bit about it now, now I just need to figure out where to look for that "holy grail"...

Getting the pinion preload and the carrier backlash (controls how the gears mesh together) is tricky. I have had problems with this in prior cars. This time I hope to find the holy grail (3.73 w/torsen) pumpkin and swap the whole thing over.

 

[DR_]

I saw one go for $500 + $100 shipping on eBay which I should have snagged. There is another salvage dealer on eBay that is currently selling the entire rear subframe w/IRS but I doubt they will get any takers. They might disassemble and sell just the pumpkin at some point.

 

[Gdyup50]

So what is it I am actually looking for if I'm searching....I'm sure it won't come up if I search "pumpkin"...LOL

I saw one go for $500 + $100 shipping on eBay which I should have snagged. There is another salvage dealer on eBay that is currently selling the entire rear subframe w/IRS but I doubt they will get any takers. They might disassemble and sell just the pumpkin at some point.

 

[DR_]

To most people differential is synonymous with the entire pumpkin even though technically the differential is inside. I would search for 2015 mustang 3.73 differential and see if it is the entire aluminum carrier, gears, and cover. All 3.73 have the Torsen and they all appear to be the aluminum carrier as well (I've only seen 2 so I'm not sure about the aluminum carrier part). The cast iron carriers are easy to spot as they are rusty.

 

[Gdyup50]

And I'm guessing it needs to be auto or is there no distinction?

To most people differential is synonymous with the entire pumpkin even though technically the differential is inside. I would search for 2015 mustang 3.73 differential and see if it is the entire aluminum carrier, gears, and cover. All 3.73 have the Torsen and they all appear to be the aluminum carrier as well (I've only seen 2 so I'm not sure about the aluminum carrier part). The cast iron carriers are easy to spot as they are rusty.

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