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Installing 3:31 in Torsen

EXP Jawa

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As far as I can tell, the old 8.8 - as a rear axle - is obsolete and no longer in production. All of the vehicles that used the 8.8 are gone, except for Mustang and F-150 which have moved on. I understand that even some of the Transit models may use the Super 8.8 as well.

That said, the F-150 still uses the old 8.8 as a front axle on 4x4 models. I haven't seen any indication that Ford will change that, but who knows?
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Tommy V

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The Super 8.8 has a lot of differences compared to the old 8.8 gear sets. The ring bolt pattern is different, though I believe that the pitch diameter of the gear is about the same. But probably more importantly, the pinion is beefier and takes a bigger bearing. So, the gear sets do not interchange in any way.

The Ford Racing catmessage d m I have (2016) doesn't show the 3.31:1 set, so if you wanted them, you'd have to order as a service part from a Ford dealer. As far as I can tell, the FR3Z-4209-D number should be the service part number (not the production number) for the correct gear set (2015-17 Super 8.8 3.31). https://lmr.com/item/LRS-4209-331/ford-331-gears-2015

Regarding the F-150, at least some of the '15+ trucks use a solid-axle version of the Super 8.8, which would take the same gearing as the Mustang IRS.
Wow thats crazy because i ordered mine out of the ford racing catalog for 2015 .The place i ordered them from screwed up the part number!!!.Just make sure they know its for a irs rear,not a soild axle rear.U will need a new crush sleeve and maybe some shims,everything eles will work.Maybe a good idea to get an extra pinion bearing incase the one u have gets messed up pressing it off.
 

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Which part is crazy? Both the old 8.8 and the new Super 8.8 have solid axle and IRS versions, so that isn't a useful delineator. And, FWIW, the ring & pinion gearing really don't care what the axle shafts look like, that has no bearing on the gearing itself. The same gear sets go into both solid and IRS variants of a given axle.
 

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Which part is crazy? Both the old 8.8 and the new Super 8.8 have solid axle and IRS versions, so that isn't a useful delineator. And, FWIW, the ring & pinion gearing really don't care what the axle shafts look like, that has no bearing on the gearing itself. The same gear sets go into both solid and IRS variants of a given axle.
Wtf areu talking about,the super 8.8 irs Gears and 8.8 soild axle ring and pinion are different period,i had them apart,i know.And when i said thats crazy i was referring to the ford racing catalog i looked at having the part number for the super 8.8 gears,so nof sure what that other crap u were shooting off about.Also the same gears do not go into super 8.8 rear as the 8.8 soild rear,unless u want to change the lockers and other shit which im sure most guys dont want to.So we dont need all the technical shit about the difference between a rear/locker and a rear housing,Get the right gears irs 8.8 in Our cars,their different then the indp 8.8
 

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I'm not really sure what you're on about, your post is a bit hard to read. All I am saying is that the Super 8.8 and the old 8.8 are different, gears not interchangeable. Sounds like we're in agreement there. I never said that the same gears can go in each.

And both the old 8.8 and the Super 8.8 axles have solid and IRS variants (but that in and of itself doesn't impact the R&P gears). So, you can't just ask for gears for an 8.8 IRS and expect that's all you need to know, because that doesn't resolve the issue. You have to make sure that if you're ordering gears for a Super 8.8, that its actually for a Super 8.8 - you can't rely on IRS vs solid. That was what I stated, and I still stand by it.

So, I'm not sure where you're coming from here.
 

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Tommy V

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I'm not really sure what you're on about, your post is a bit hard to read. All I am saying is that the Super 8.8 and the old 8.8 are different, gears not interchangeable. Sounds like we're in agreement there. I never said that the same gears can go in each.

And both the old 8.8 and the Super 8.8 axles have solid and IRS variants (but that in and of itself doesn't impact the R&P gears). So, you can't just ask for gears for an 8.8 IRS and expect that's all you need to know, because that doesn't resolve the issue. You have to make sure that if you're ordering gears for a Super 8.8, that its actually for a Super 8.8 - you can't rely on IRS vs solid. That was what I stated, and I still stand by it.

So, I'm not sure where you're coming from here.
I agree with that,and maybe i misinterpted what u were saying.The only difference i saw in the ford racing catalog was the super 8.8 gears for the irs had the letter a at the end of the part number.Im pretty sure their are a couple different part numbers for the gears.I found out the hard way,had mine all torn down and when i went to put the ring gear on the torsen i was like WTF..The part number in the book were right the company that shipped them screwed up the number.All's good man
 

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Yeah, unfortunately, Ford is rampant with part numbers. First, there is the production part number (probably starts with CR3W for some of these), then there is a different number for service parts (the CR3Z), then on top of that Ford Racing/Performance assigns their own number (M-etc). Some of the FRPP numbers have suffixes that make sense, some probably just made sense at the time. Then, for 3rd party parts (like the Torsen), the vendors has their own part number, which may or may not be on the assembly. I'm not sure if Ford still makes their own R&P gearing in-house, or if those comes from Linamar like their normal differentials do.

So its easy to see why someone might get confused...
 

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Yeah, unfortunately, Ford is rampant with part numbers. First, there is the production part number (probably starts with CR3W for some of these), then there is a different number for service parts (the CR3Z), then on top of that Ford Racing/Performance assigns their own number (M-etc). Some of the FRPP numbers have suffixes that make sense, some probably just made sense at the time. Then, for 3rd party parts (like the Torsen), the vendors has their own part number, which may or may not be on the assembly. I'm not sure if Ford still makes their own R&P gearing in-house, or if those comes from Linamar like their normal differentials do.

So its easy to see why someone might get confused...
Yup the gears i ordered out of the fr catalog started with an M- then when i called ford they gave me a completly different number,at that point my car was on a lift with diff torn apart and i just bought a complete assy.After i got everything put back together i figured out what the correct part numbers were,at first though i didnt know their was a difference between the two lol.Oh well hopefully my pain will help the next guy get the right parts.
 

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Thanks for posting up on this, I want to switch to 3.31 but don't want to use the auto diff version (heard its weaker than the manual case).

What exactly is the part number(s) I need to order to do the swap?
 
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Thanks for posting up on this, I want to switch to 3.31 but don't want to use the auto diff version (heard its weaker than the manual case).

What exactly is the part number(s) I need to order to do the swap?
Just received my ring/pinion from LMR. Part number is FR3Z-4209-D.
 

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Tommy V

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Yep that is the number ford gave me when i called them.More then likely u can reuse your shims and bearings,u will need a new crush sleeve to set the preload.You should be able to use your shims that are in the case now for pinion debt and backlash but make sure u check these measurments just incase a shim needs to be changed.As long as you use ford gears and your orginal housing everything should work with what was in the case already.Extra tip if u dont have a press and bearing separator get an extra pinion bearing incase the one u have to take off gets damaged.
 

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Thanks for posting up on this, I want to switch to 3.31 but don't want to use the auto diff version (heard its weaker than the manual case).

What exactly is the part number(s) I need to order to do the swap?
Auto diff was 3.15.
 

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FRPP does not have a Super 8.8 in 3.31

The Super 8.8 options are 3.55, 3.73, and 4.09
Yes they do im looking at the frpp catalog right now and the # is m-4209-88331a.
 
 




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