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Aluminum vs cast iron differential

luc

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My understanding is that the aluminum went behind automatics and cast behind the manuals
Any insight as to why?
I have a 17 Pp1 and it would be a good way to drop some weight
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NGOT8R

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My understanding is that the aluminum went behind automatics and cast behind the manuals
Any insight as to why?
I have a 17 Pp1 and it would be a good way to drop some weight
Be mindful that if drag racing on sticky tires, the ears can break off on the aluminum diffs. There are pics on here of the carnage.
 

ice445

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Simple answer is that the manual cars needed a stronger diff because it's easier to shock the driveline in a manual car, and Ford can't really do anything about that (other than make the gears taller lmao). With the automagic, the computer is controlling all the shifts and it's much less abusive to the driveline, plus there's no potential for a hella clutch dump or anything like that.

All the diffs suck though, the shitty bolt design will usually fail before the case.
 

Cobra Jet

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Going from memory, I think the 2015-2017 GT PP MT82 pumpkins were supposedly iron w/optional Torsen, while the 2015-2017 GT w/ 6R80 was iron with standard trac-lock. The 2015-2017 iron case was bare, so if looking at it, the case will be “rust” color.

2015-2017 EB 6R80 or those with MT82 were strictly aluminum case w/ standard traction lock.

There were many options for the 2015-2017 rear pumpkin depending on the platform chosen. So I am not sure if I’m covering all available case/gear types....

The 2018+ GT or EB PP’s all come with iron pumpkins and Torsen. The 2018+ iron case will be coated black with a cast aluminum rear cover. Also to note, the 2018+ GT/EB PP rear covers will have the included threaded port for the rear axle temp sensor.

A) The 2018+ GT w/ MT82 came w/ Torsen and 3.73’s.

B) The 2018+ GT or EB w/10R80 came w/ Torsen and 3.55’s.

The main difference between ALL S550 pumpkins will be the rear pinion flanges between a MT82 and those of the 6R80/10R80 pumpkin. From what I can remember if buying a complete used or new pumpkin w/X-gears, you should not get a MT82 pumpkin for a 6R80/10R80 and vice versa... the rear pinion flange would have to be swapped to mate with X-trans.

Other notes for all S550’s:
1) The physical pumpkin and mounting points are the same between all S550’s, it’s just the rear pinion flange that will vary based on what trans it was associated with (or going to be mated to if swapping rears).

2) Due to the variance in the rear pinion flange, you must source the correct driveshaft because the front trans flange coming off the trans (MT82, 6R80, 10R80 or Tremec) will have to match to the proper driveshaft.

3) I haven’t dealt with any 3.15’s, however from what I can recall (and based on many threads), if the car has a factory 3.15 pumpkin, the gear ratio can’t be easily changed (or requires more R&R hoops to jump through) due to the 3.15 pumpkin interior sizing. Don’t quote me on this, because I’m not 110% certain of the exact issue - but from what I’ve seen, most who have a 3.15 just get a complete pumpkin w/X-gearing for their application.


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.


//////////////////////////////

If buying a used S550 pumpkin from unknown sellers (off this site) - be careful. Some of the early S550 pumpkins were warranted out due to premature internal gear wear or pinion failures. Probably more prevalent with the 2015-2016 “vibe” issue (huge thread in Issues/TSB forum for those who want more info).

Buy from reputable Sellers or support the Vendors on this site who sell brand new loaded pumpkins.
 
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andrewtac

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The 3.15 diff is a different size, but the dimensions of the pumpkin are the same. If you want to change the gear from 3.15 you need a different diff and same going from another size to 3.15
 

TeeLew

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I think if you're drag racing, particularly on slicks, you should be on an iron differential housing. If you're not a Rock-ape doing clutch drops, though, I bet the aluminum housing would be just fine, even for road race duty.
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