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Differential Flanges - Any Experts?

StrongFord

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I have a 2015 GT manual with 3.31 ratio and cast iron housing. I purchased a used differential from a 2018 GT manual (verified in person) with 3.55 ratio and cast iron housing. Everything I have found indicates there are only two available flange options from Ford, one for manual and one for automatic - regardless of model year (2015-2018).

The 2018 flange has about a 1/8" smaller inside diameter than my 2015 flange. The 2018 flange also has a taper at the top where my 2015 flange does not. The driveshaft will not press into the pinion flange. The 2018 flange has a Ford part number HR3W-4851-BA printed on it. The 2015 flange is too rusted to find a part number.

I could swap the flanges, but since they are both manuals and supposedly they should mate, I did not want to jump into another project without knowing if it's necessary. Ultimately I put my 2015 differential back into the car.

What the flange is going on here? Anyone encounter this issue?

IMG_4338.JPG


Note the taper at the top of the flange. The driveshaft and flange are hard contact. They could not be pulled together any further than this point. The driveshaft should insert as deep as the window opening.

IMG_4345.JPG

IMG_4341.JPG
IMG_4349.JPG

The caliper was set to the I.D. of the 2018 flange. You can see how much smaller it is than my 2015 flange.
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JohnVallo

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I assumed that all 2015-up differential flanges for Mustangs were categorized as either Automatic or Manual
apparently that is not the case.

Here's some compatibility info on the Pinion Flanges:
-2015-2017 Mustang with MT82 use 113mm pinion flange, 95mm bolt circle.
-2015-2020 Mustang w/ Automatic Transmissions use 110mm pinion flange, 93mm bolt circle.
-2018-2019 Mustang w/ Manual Transmissions use 110mm pinion flange, 93mm bolt circle.
-2015-2020 Shelby GT350 (Manual Transmission) use 110mm pinion flange, 93mm bolt circle.

I can offer some facts for the GT350's as I own a 2016 GT350 and have acquired 2 spare 2016 GT350 complete carriers, as well as 2 spare 2017 GT350 carriers
All flanges on these GT350's measure right at 110mm span.
I did purchase the new 2018 manual flange, pn: HR3Z-4851-B
This flange has the same dimensions as all my other GT350 flanges
One observation I have noticed is that all pre 2018 flanges did NOT come painted from the factory.
The new HR3Z-4851-B flange comes painted black and seems to be a higher quality nicer looking piece.

Here is the new 2018 flange HR3Z-4851-B
IMG_0506-1200.jpg

IMG_0507-1200.jpg


The span on this new flange is right at 110mm
IMG_0504-1200.jpg


The bolt circle looks to be right at 93mm diameter

IMG_0505-1200.jpg
 
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StrongFord

StrongFord

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I have (2) 2016 manual carrier assy's, and (2) 2017 manual carriers.
All measure right at 110mm (where your measurement is)

Hope this helps...
Well, that's interesting, I measured my 2018 flange and it's right about 110mm. I can't measure the 2015 flange it's reinstalled. Judging by my estimate that it was about 1/8" larger I'd say it's around 113mm. So maybe my original 2015 flange is the odd one.

Do your flanges taper in near the top like black one in the 2nd picture?

Thanks!
 
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Because of the drivetrain vibration issues from the 15 to 17 cars, the 18 and ups have a revised pinion flange and different driveshafts. The older shafts will not work with the newer flanges.
 

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Also, PSA: GT350 diffs also have a different, and smaller flange (looks like the same as the 18 manual one you posted here) that I am not able to bolt up my 2015 manual driveshaft too. Bolt circle and flange ID are smaller. This came as a real surprise bummer today for me.
 

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Yup can confirm what BMac said above. I was there with him and did the measurements. 2015 pinion flange has a approximately 112mm ID while the GT350 had about 110mm ID. Tried to pull it in with bolts on opposite sides of the driveshaft but i could not get the second bolt started because the holes did not line up when the first screw was started.
 
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Also, PSA: GT350 diffs also have a different, and smaller flange (looks like the same as the 18 manual one you posted here) that I am not able to bolt up my 2015 manual driveshaft too. Bolt circle and flange ID are smaller. This came as a real surprise bummer today for me.
I haven't shared to the forum yet, but some lessons learned from this experience. A driveshaft is required to accomplish the swap. Contrary to the online information I was able to find, the driveshaft and pinion flange changed for 2018. Likely for the GT350 too.

Here's the 2015 GT driveshaft compared to a 2018 GT that I bought. I installed the 2018 3.55 differential and driveshaft yesterday.

Driveshaft compare.JPG
Driveshaft CV.JPG
CV Joint.JPG
 

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I am running into this same issue today. I bought a 3.15 pre-2018 diff with the correct manual flange but the flange was damaged in shipping. I bought a used one online but it turned out to be the smaller diameter one. I checked with an oem online system and it shows the same part number for the pre and post 2018 flanges (FR3Z-4851-B). The larger diameter flange from my car has a part number of FR3W-4851-FC but I can't find that part number online. Very aggravating!
 

BmacIL

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I will probably be swapping flanges instead of buying a new driveshaft. More economical.
 
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StrongFord

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I will probably be swapping flanges instead of buying a new driveshaft. More economical.
Not having the proper tools or experience torquing the pinion nut, nor wanting to pay a shop to do the swap led me this way. This way I still have my factory differential fully intact in case I needed to swap back or consider selling it.
 

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BmacIL

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Not having the proper tools or experience torquing the pinion nut, nor wanting to pay a shop to do the swap led me this way. This way I still have my factory differential fully intact in case I needed to swap back or consider selling it.
Yeah I'm planning on the same, but buying a new flange (or used if necessary), nut, seal and crush spacer, and changing out the one on the new diff, leaving the current one intact. I'll have someone do that for me and then I'll install it myself.
 
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StrongFord

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Yeah I'm planning on the same, but buying a new flange (or used if necessary), nut, seal and crush spacer, and changing out the one on the new diff, leaving the current one intact. I'll have someone do that for me and then I'll install it myself.
So, did you reinstall your original differential while you get more parts? I did, I pulled the original and mounted the new one only to find it didn't fit :facepalm:. Then reinstalled my original for a few weeks and did the whole job again, now with a driveshaft.

Just for good measure check your rear wheel bearings. My driver's side was totally shot, those got changed too.

Good luck
 

BmacIL

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So, did you reinstall your original differential while you get more parts? I did, I pulled the original and mounted the new one only to find it didn't fit :facepalm:. Then reinstalled my original for a few weeks and did the whole job again, now with a driveshaft.

Just for good measure check your rear wheel bearings. My driver's side was totally shot, those got changed too.

Good luck
Yes, I did have to reinstall my OE 3.31. I was very unhappy about that. While I was in there I did check wheel bearings and both seemed fine. I did change to the new axle nuts with the 150+1/8 turn spec and some red loctite. They were popping a lot before.

My least favorite part of it is that the exhaust has to come off. I love the sound, but damn the corsa catbacks are a PITA to install/remove.
 

BmacIL

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So, did you reinstall your original differential while you get more parts? I did, I pulled the original and mounted the new one only to find it didn't fit :facepalm:. Then reinstalled my original for a few weeks and did the whole job again, now with a driveshaft.

Just for good measure check your rear wheel bearings. My driver's side was totally shot, those got changed too.

Good luck
Scratch my above post. I think I'll end up getting a 2018+ one piece driveshaft. Just need to confirm that this GT350 flange is the same as the 2018+ flange. Looks identical and the measurements I took mirror what you found. If I'm going to swap out the shaft, might as well get something with an upgrade.
 
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StrongFord

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Scratch my above post. I think I'll end up getting a 2018+ one piece driveshaft. Just need to confirm that this GT350 flange is the same as the 2018+ flange. Looks identical and the measurements I took mirror what you found. If I'm going to swap out the shaft, might as well get something with an upgrade.
Awesome, you’re always going the extra mile.

The OD of the driveshaft CV was 108mm and the pinion flange ID was 110mm. The overall driveshaft length between 2015 and 2018 is the same or at least really close. An exact measurement was tough with CV movement.

I would think a 2018+ one piece driveshaft would be a direct fit with this flange.
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