Rear end damage

[Fordman]

Brett at FenFab has a rear diff brace almost ready to go for the single bolt ST’s.

This would be great news! The stupid one bolt rear diff Is what is keeping me from doing a ZFG tune. To be honest, if I had know about the one bolt diff change on the 2021‘s, I probably would not have bought one.
Please post if you find any info about the FenFab rear diff brace.

 

[GearHead_1]

Brett at FenFab has a rear diff brace almost ready to go for the single bolt ST’s.

Yeah, I'd take a look at that.

 

[Clears]

I would definitely be all over that as well!

 

[jrgoffin]

Pic he posted. Very strange that Ford would have made the change to the single rear bolt, especially since the differential cover is still cast for the two.

 

[TONYROD805]

WHO IS THIS FROM

 

[TMac]

Pic he posted. Very strange that Ford would have made the change to the single rear bolt, especially since the differential cover is still cast for the two.

View attachment 8460

I'm going to assume this is a prototype. If not, my opinion is the slotted holes being used to mount the "brace" to the differential are problematic. Think about the differential's movement under torque- it's going to want to rotate upwards from the driveshaft end and downward from the rear view (we'll ignore any right-left "twist" due to gear engagement). Therefore, the downward movement of the diff is not limited due to the slotted mounts. It looks as if it's using some sort of bushing (the red part). A bushing like that should work under a compression load, not tension.

 

[jrgoffin]

WHO IS THIS FROM

See post #20. And 21 & 22.

I'm going to assume this is a prototype. If not, my opinion is the slotted holes being used to mount the "brace" to the differential are problematic. Think about the differential's movement under torque- it's going to want to rotate upwards from the driveshaft end and downward from the rear view (we'll ignore any right-left "twist" due to gear engagement). Therefore, the downward movement of the diff is not limited due to the slotted mounts. It looks as if it's using some sort of bushing (the red part). A bushing like that should work under a compression load, not tension.

No idea. Just shared the picture I saw. My '20 has all four bolts so it's not an issue. Hopefully those that are inflicted by the change will find some relief.

 

[TMac]

See post #20. And 21 & 22.
No idea. Just shared the picture I saw. My '20 has all four bolts so it's not an issue. Hopefully those that are inflicted by the change will find some relief.

Well they won't find any relief with that design. I've seen other examples of the FenFab stuff and it's very well done, but I don't think they thought enough about that mount, because the rotation of the differential is in the opposite direction of what that product is designed for.

 

[GearHead_1]

No there is no hole in the sub-frame and consequently no bushing.

 

[sadeen]

No there is no hole in the sub-frame and consequently no bushing.

Well, that pretty much sucks. WTF? Thanks.

 

[GearHead_1]

I suspect that the penny counters at Ford look at these vehicles as we can cut a penny here as it shouldn't be problematic with the power levels these vehicles leave the factory. They don't look at these vehicles and how they hold up to really being driven hard or modified.

 

[bluesnake01]

Might be Ford's way of catching modders easier? Seems like its been more common with people who are tuned.

I think only one person with a stock car had this happened to them but that was due to towing with the sensors on I believe.

 

[TMac]

I don't think Ford purposely cheapened a part to catch "modders" just so they could pay out thousands in warranty claims! When that differential carrier bolt fails, it's a nightmare for the entire driveline from the driveshaft rearward.

 

[jrgoffin]

Well they won't find any relief with that design. I've seen other examples of the FenFab stuff and it's very well done, but I don't think they thought enough about that mount, because the rotation of the differential is in the opposite direction of what that product is designed for.

The only way to really fix this issue is to replace the subframe with the earlier design that allowed for both bolts. I just can't imagine Ford purposely deleting one bolt in an area where it is sorely needed. Maybe it was a supplier screw-up and the powers-that-be decided to use what they had just to keep production running. Of course they will pay for it in some instances, but there are probably a large amount of vehicles out there that won't have any problems. All about $$$$$.

 

[TMac]

It's all just conjecture. But bear in mind the fragmented production environment of the 2021 models.

It is equally likely that the re-engineered version is perfectly fine, but a batch of bolts weren't heat treated correctly causing them to fail. Or that the anecdotal evidence from the people who've experienced the problem was misstated so as to cover their ass for their own negligence. Or, an engineer seeking a bonus found a way to save a few bucks but screwed up a simulation/math. Or a supplier had Covid issues which forced a quick change.

Until you see dozens of these fail, it's hard to come to a conclusion. But, when you look at the amount of money it takes to correct the ensuing assembly failures, it's hard for me to believe that Ford did this for some nefarious purpose.

However, if you have a single bolt diff and someone engineers a solution for it, good for them.

 

[UNBROKEN]

I’d just like to clarify for everyone that thinks they only have a single bolt…you have 3. There are 2 more on the front.

 

[jrgoffin]

Actually, and from some easy digging, it appears this "single-bolt" subrame is the one used in the base model Explorers that don't have the power of the ST. Here is one I found online from a 2.3 Explorer:



When I put my VIN in the Ford parts system (or searched for all ST models), the "dual-bolt" subframe is still the only one listed. Granted, the Ford catalog can be full of errors, but I imagine the weaker version being used is a screw-up at the plant. Somehow, these got mixed in, rather than it being an "updated" part.

I’d just like to clarify for everyone that thinks they only have a single bolt…you have 3. There are 2 more on the front.

Yes, there are two more mounted vertically on either side of the differential housing.

 

[TMac]

That is a great find @jrgoffin ! Points out that there is a good possibility of a supplier issue so they substituted the subframes. So they might have bypassed the engineering dept. to get the cars out.

 

[Fordman]

I wonder if they had a supplier shortage of the 4 bolt ST version, and installed the 3 bolt version to keep up production, the demand for the ST is pretty high?

 

[Fordman]

Sorry TMac, you posted while I was typing.