Other gear ratios in 3.15 housing - Torsen or LSD

[veeefour]

So many questions...so little answers

Looking for higher gear ratio - standard GT with AT comes with 100% alu housing and 3.15 ratio. Half shafts are specific as well.

Is it possible to swap the gears only in ALU housing or do I need to swap the clutch pack as well? If I need to swap the pack then maybe I can fit the Torsen pack at the same time. Torsen with AT anybody?

All EU spec GT stangs comes with 3.55 cast iron pumpkin either for MT or AT.
I can get the whole used assy locally from EU spec car - mostly form MT models. The question is would the 3.15 half shafts fit the cast iron pumpkin?

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[stang1971]

nope.... 3.15 only in that housing..... it sucks....

 

[veeefour]

Thx.

I will buy the whole cast iron assy then - the question is do I need to swap the half shafts as well?

 

[EXP Jawa]

Well, understand that the axle housing (sometimes called the carrier) and the differential housing (often called a carrier) are two separate things that just happen to work for the same employer. This tends to confuse people, and could lead to an entire side discussion about axle terminology. But I spare you that now.

The aluminum axle carrier has the same interface dimensions as the iron one. Both attach to the subframe the same, and the differentials and such attach to both the same. You can install either version of the differential in either axle carrier, assuming you do so with the appropriate gear ratio set. The differential itself, which of course the ring gear bolts to, has to be the correct version to use the 3.15:1 gearing. The big difference is the .3" difference in ring gear flange location on the differential carrier/body/housing, which allows for the gear to be spaced farther back from the pinion (so the pinion can be bigger in diameter). The rest of the axle assembly should be transparent. You can install higher numeric gear ratios into the aluminum axle carrier as long as you swap the diff carrier with it. And you can substitute 3.15 gears (and diff carrier!) into the iron housing, like people are doing for FI cars. The rest of the parts should fit up the same.

 

[veeefour]

Rick,

Thanks for the explanation - I understand what are you trying to say as I'm a design engineer.
You are of course correct but this is mostly "semantics" which 90% of people will never be able to understand

Now, the facts. You reckon both housings are 100% the same in dimensions?

So this means I can just buy:

-2015-2017 MUSTANG 8.8-INCH TRACTION-LOCK DIFFERENTIAL - M-4204-M Retail $199.00
-8.8" 3.55 RING GEAR AND PINION M-4209-88355 - Retail $259.00

For this I would also need:

-2015-2017 MUSTANG AUTOMATIC IRS PINION FLANGE - M-4851-M8A Retail $79.00
-RING AND PINION INSTALLATION KIT SUPER 8.8" IRS - M-4210-B3 Retail $169.00
-plus oil and friction modifier
-plus a shitload of labor which I can do it myself

2015-2017 MUSTANG SUPER 8.8" IRS LOADED DIFFERENTIAL HOUSING 3.55 - M-4001-88355 $899 in Summit plus shipping...
not sure I want to spend 2-3 days cracking open the diif just to save 200 bucks...

 

[Jay-rod427]

Rick,

Thanks for the explanation - I understand what are you trying to say as I'm a design engineer.
You are of course correct but this is mostly "semantics" which 90% of people will never be able to understand

Now, the facts. You reckon both housings are 100% the same in dimensions?

So this means I can just buy:

-2015-2017 MUSTANG 8.8-INCH TRACTION-LOCK DIFFERENTIAL - M-4204-M Retail $199.00
-8.8" 3.55 RING GEAR AND PINION M-4209-88355 - Retail $259.00

For this I would also need:

-2015-2017 MUSTANG AUTOMATIC IRS PINION FLANGE - M-4851-M8A Retail $79.00
-RING AND PINION INSTALLATION KIT SUPER 8.8" IRS - M-4210-B3 Retail $169.00
-plus oil and friction modifier
-plus a shitload of labor which I can do it myself

2015-2017 MUSTANG SUPER 8.8" IRS LOADED DIFFERENTIAL HOUSING 3.55 - M-4001-88355 $899 in Summit plus shipping...
not sure I want to spend 2-3 days cracking open the diif just to save 200 bucks...

I would buy the complete assembled version. $200 and no messing with setting up the gearset.

 

[EXP Jawa]

I'd second that. $200 is not nothing, but installing and setting up R&P gears properly is not nothing either. It takes a bit of skill, and if done wrong will result in gears that are noisy. Swapping the factory-assembled axle carrier is far, far easier.

 

[veeefour]

Then again for that money I could buy gears and Torsen diff...hmmm Torsen is very tempting.

How about 3.55 gears and Torsen in alu housing!

 

[veeefour]

Oki doki, here's a confirmation that you can put everything you want in ALU case - as Rick mentioned they are identical in size:

http://www.stangtv.com/tech-stories...end-build-and-upgrades-with-ford-performance/

As for me a decision has been made: Torsen, 3.55 gears and a shitload of labor :doh:

 

[veeefour]

Crap...lead time for Torsen is over 2-3 weeks...LSD is stock...

Now wait for Torsen or get the limited slip which is significantly cheaper?

Added a poll TORSEN vs LSD - please vote!

 

[69mach1-395]

What will you use for? IIRC, the torsen is better for curves and the lsd for straights?

 

[veeefour]

At the end if the day I decided to buy 3.55 gears plus Ford installation kit, did everything myself:

Plus the best diff at the market - Wavetrac:

Alu or iron case - they are identical. 3.15 gears are also identical and the diff from 3.15 is also identical - why Ford says it will not fit other gear ratios?
It will fit but I reckon it will not work as the clutch packs are just too weak. Wavetrac makes a night and day difference. AT with 3.55 is a ROCKET!

 

[EXP Jawa]

The differentials for the 3.15:1 gears are not identical to the others. As I stated above, there is a .3" difference in the location of the ring gear flange. If you set the two diffs next to each other before the install, you'd see it. That might not sound like much of a difference, but if you put 3.55 gear on it, you will never ever get them shimmed correctly.

Regarding best diff on the market, well, I think that's still open for debate. But still, I'm glad this came together for you. It at least sets a precedent for what needs to be done for future gear swaps. So, good information.

 

[veeefour]

Well, I did not bother to measure them with caliper but they really look identical. There are approx 7mm shims on both sides of the diff so I through it's doable as it seems like plenty.

 

[whatsup62]

Another thing in "not" being identical.
Aluminum is not Steel.
Depending what you are going to do with it the Aluminum housing is not as strong.
A few guys have busted them.

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