Is there a difference between 15-17 and 2018 3.15 Differential ??

[Myshelby3425]

Does anyone know if there is a difference between the 15-17 3.15 diff and the 2018 3.15 diff? I’m looking to swap over to a 3.15 SC setup and wanted to just buy the full pumpkin with gears since it would be spot cheaper vs having someone install gears. This will be going on a 18 A10 GT

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[Anthony 05 GT]

I'm pretty sure they are the same, but the '15-'17 autos had aluminum housing while manuals had cast iron housing which are stronger. Not sure on the '18

 

[CNCLester]

I'm in the process of putting my diff from a 16 in my 18 manual pp gt for the gear swap. My 18 pinion flange has a bolt circle 2 mm smaller in diameter than the 16 diff. Had to order another 18 pinion flange. It should be here tomorrow.
I do not know if the 18 automatic flange is different than previous s550 auto's or not.

 

[Cobra Jet]

I'm pretty sure they are the same, but the '15-'17 autos had aluminum housing while manuals had cast iron housing which are stronger. Not sure on the '18

For the 2015-2017:
Also there is a difference with the pinion flanges between a 6R80 (aluminum case) and the MT82 (iron case). So be sure to verify that you’re buying a rear that has the correct flange for your application, otherwise you’ll be spending additional money for a flange kit and then the time needed to swap it.

For the 2018/19:
Depending on if you are buying new or used, the Performance Pack equipped Mustangs all now have a Torsen rear with 3.73’s (GT) or 3.55’s (EB or GT) and the cases are iron regardless if the trans is the new 10R80 or the MT82. Again, be aware of the auto vs. manual trans rear diff pinion flanges. Another thing to be aware of for 2018/19 rear diffs, if it matters to you - the 2018/19 PP rear diff cover is predrilled for the rear axle temp sensor. I’m not sure if the diff cover on a 2018/19 w/3.15’s even has the sensor.

As far as physical mounting points, they are the same regardless of model year. There may be driveshaft variances as well between the model years and trans options, so be sure to research that too.


TIP:
- If the rear diff has Trac-loc guts, you won't be able to see through it with axles removed. There will be a "bar" in the hole which is for the spider gears.

- If the rear diff has Torsen guts, you'll be able to see through it with axles removed.

 

[Myshelby3425]

For the 2015-2017:
Also there is a difference with the pinion flanges between a 6R80 (aluminum case) and the MT82 (iron case). So be sure to verify that you’re buying a rear that has the correct flange for your application, otherwise you’ll be spending additional money for a flange kit and then the time needed to swap it.

For the 2018/19:
Depending on if you are buying new or used, the Performance Pack equipped Mustangs all now have a Torsen rear with 3.73’s (GT) or 3.55’s (EB or GT) and the cases are iron regardless if the trans is the new 10R80 or the MT82. Again, be aware of the auto vs. manual trans rear diff pinion flanges. Another thing to be aware of for 2018/19 rear diffs, if it matters to you - the 2018/19 PP rear diff cover is predrilled for the rear axle temp sensor. I’m not sure if the diff cover on a 2018/19 w/3.15’s even has the sensor.

As far as physical mounting points, they are the same regardless of model year. There may be driveshaft variances as well between the model years and trans options, so be sure to research that too.

I’d be swapping the full diff. It’s a complete aluminum diff from 15-17. Would it still matter about the pinion flanges or would I just need to worry about the mounting point for the drive shaft?

 

[Cobra Jet]

I’d be swapping the full diff. It’s a complete aluminum diff from 15-17. Would it still matter about the pinion flanges or would I just need to worry about the mounting point for the drive shaft?

Yes rear diff flange matters - because the FLANGE has to be for the same type of transmission from the doner to your vehicle.

If yours has an auto transmission, a rear diff with a flange for a manual trans won’t work (and opposite is true). This applies to all S550s, regardless of model year.

 

[drabon74]

Does anyone know if there is a difference between the 15-17 3.15 diff and the 2018 3.15 diff? I’m looking to swap over to a 3.15 SC setup and wanted to just buy the full pumpkin with gears since it would be spot cheaper vs having someone install gears. This will be going on a 18 A10 GT

Pm me if you have the 3.55 and are interested in trading. I have the 18 a10 3.15 auto with everything you will need.

 

[Myshelby3425]

Yes rear diff flange matters - because the FLANGE has to be for the same type of transmission from the doner to your vehicle.

If yours has an auto transmission, a rear diff with a flange for a manual trans won’t work (and opposite is true). This applies to all S550s, regardless of model year.

True, thanks. Is there anyone that can verify if the 18 and 15-17 share the same pinion flanges for the auto trans?

 

[zrwhat]

Yes, right when u need the answer u were actually looking for no response.

Anybody have an answer for this? I have a 3.55 2017 6R80 that I want to go to 3.15. Local yard has a low mile 2018 3.15 AT Ecoboost housing for next to nothing. Thanks!

 

[EFI]

I thought the 3.15 pumpkin was different on the 15-17 and only came on the V6. The 3.31, 3.55 and 3.73 diffs were different and not compatible with the 3.15 ones.

So I'm pretty sure you can't go with a 3.15 from a 15-17, but you can use the other 3.

 

[K4fxd]

The pumpkin is the same. The differential is offset differently in the 3.15

Tasca shows 2 flange part numbers. 1 for auto, 1 for manual (15 to 17)
Its called a companion flange. Here is the part number for the 17 manual.
Companion Flange - Ford (HR3Z-4851-B)



Shows shows only 1 part number for auto and manual. 18+
My links are dead and it is not an easy search.

M-4851-M8A
2015-20 Mustang 110mm IRS Pinion Flange Kit - 6R80/10R80/MT82 Transmission

 

[Brazos609]

Anybody have an answer for this? I have a 3.55 2017 6R80 that I want to go to 3.15. Local yard has a low mile 2018 3.15 AT Ecoboost housing for next to nothing. Thanks!

Yes, yuh our 17 auto and a 18 auto were both equipped with small flange differentials.

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