Check this NOW if you have a 2021 Bronco -- cracks on rear control arm upper brackets

[BAUS67]

@popo_patty

Careful now there has been plenty of crack in B6G land in the past.

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[Oldhippie]

‘23 Big Bend 2dr 2.7 Sasquatch w/tow 3” lift low miles Only 3 off road trips so far…

 

[87-Z28]

Good thread @popo_patty. Interesting stuff. Some thoughts on how energy gets transferred through the rear links and into the end mounts that are cracking.

The oem bushings on the rear links are compliant in the sense that the material will deform (strain) allowing for motion and rotations and thereby providing some extra articulation from the “rigid” links. These deformations in the bushings allow for some of the shock energy from dynamic loading to be absorbed in the form of deformation or strain energy. This reduces the shock transfer to the frame but at the cost of articulation. The bushings need to deform under stress which limits compliance based on stiffness.

The fancy after market end links with Johnny joints allow for freedom of movement or rotation without much resisting stress. This enhances articulation but comes at the cost of limited strain energy absorption. The bushings are stiffer and allow for low friction sliding that produces no significant shear strain or deformation, only minimal compressive strains. And thus they usually transfer greater shock loads.

The metal on metal heim joints have virtually no compliance and don’t absorb any significant strain energy.

not saying the aftermarket end links are good or bad just how they transfer energy.

 

[Felix808]

Careful now there has been plenty of crack in B6G land in the past.

That's just wrong. How am I suppose to unsee that

 

[edgarmcgauley]

So I am noticing 50149AF stamped on the open design and 50149AG or 50149AH on the closed ones.

 

[redone17]

Good thread @popo_patty. Interesting stuff. Some thoughts on how energy gets transferred through the rear links and into the end mounts that are cracking.

The oem bushings on the rear links are compliant in the sense that the material will deform (strain) allowing for motion and rotations and thereby providing some extra articulation from the “rigid” links. These deformations in the bushings allow for some of the shock energy from dynamic loading to be absorbed in the form of deformation or strain energy. This reduces the shock transfer to the frame but at the cost of articulation. The bushings need to deform under stress which limits compliance based on stiffness.

The fancy after market end links with Johnny joints allow for freedom of movement or rotation without much resisting stress. This enhances articulation but comes at the cost of limited strain energy absorption. The bushings are stiffer and allow for low friction sliding that produces no significant shear strain or deformation, only minimal compressive strains. And thus they usually transfer greater shock loads.

The metal on metal heim joints have virtually no compliance and don’t absorb any significant strain energy.

not saying the aftermarket end links are good or bad just how they transfer energy.

Having me second guessing the install of the MetalCloak uppers I recently acquired…

 

[popo_patty]

Having me second guessing the install of the MetalCloak uppers I recently acquired…

If you’re boxed there are no documented failures. I’ve seen the failure now on multiple different styles of aftermarket and even a few stock arms

 

[redone17]

If you’re boxed there are no documented failures. I’ve seen the failure now on multiple different styles of aftermarket and even a few stock arms

Early 21 build. I’ll get a peek under there next week when I wash all the salt off.

 

[kodiakisland]

I'll try to get it clean enough to look next week. I've got an early 21, so I won't be surprised to find something not so nice.

 

[huey]

And someone brought up to me that the frame dates of manufacture don’t necessarily coincide with the bronco date. So a later bronco could get an early frame or something like that. This could be the answer

This is correct, the date the frame is made is not the same as the day the truck rolls off the assembly line. Even with a hurried launch it will take days to get a finished frame to Ford assembly and then built into a vehicle.

So far it seems the issues are 21 broncos only so I would guess there was an early rev change. I have some thoughts on this but will see if I can find some history on changes to that part first.

For those worried about rust, well that's gonna happen. When the welds are laid down a shielding gas is used which is a mixture or argon & co2. The weld wire contains silica, during the weld it is not uncommon for shielding gas to combine with the silica which then floats to the top as an oxide. These oxide "islands" are known to prevent good adhesion to the protective paint, which is why we see rust. Fear not, you can look under vehicles built by BMW, Mercedes, Ford etc and they will all have rust on the frame or cradle. Even when they only have a 500 miles.

Or more simply, you could trail your truck, hit a rock and knock the paint off. Rust is gonna happen on the frame.

 

[Donkeygyrl]

Have welder buddy box yours in he does great welds.

 

[JojoReady]

Here are the build date breaks for the 2.7. Don't know what physical changes were done but the first version was not quite two months 5/3/21-6-24-21.

I wonder if the change to the box design coincided with the addition of rear sway bar end link brackets. The timing seems about right.

 

[redone17]

I wonder if the change to the box design coincided with the addition of rear sway bar end link brackets. The timing seems about right.

I was thinking the same thing. I hoped Barnes made sway bar brackets. I asked them if it was in their future.

 

[87-Z28]

Having me second guessing the install of the MetalCloak uppers I recently acquired…

no. I wouldn’t worry about it. The Johnny joints are great for articulation. That trumps the minor shock transmission concerns in the rear links.Just some engineering design thoughts. Not quantified so not even sure how much energy absorption the oem bushings provide. Depends greatly on actual material properties.

 

[Bird Dog Off Road]

Hey ya'll, I know this has been addressed here and there but I want to bring this fully into the light with some research i've done.

The rear, control arm upper brackets on my 21 Bronco are cracked... Both sides in multiple places. My welding friend stop drilled and welded up one crack but I have since discovered another and also on the passenger side. To access and repair the passenger side I will have to drop the tank to assess which we will do soon. I reached out to a few friends that also have 21 Broncos and 3 of them have cracks in the same spot with others checking for me tonight. So far all 4 of us with cracks are modified with aftermarket, rear arms, 37's and we wheel hard and often. I'm still looking to see if unmodified 2021 Broncos have this crack but so far no.

I did find a friend with a 21 Bronco Sasquatch that is stock and he has no visible cracks, but the welds are now rusting right where I've seen some of the cracks form which leads me to believe his is on the way out as well.

I posted up in my group asking for photos of newer Broncos and someone with a 23 Bronco sent me this awesome photo. If you compare, you can see the newer Bronco's have boxed in that upper bracket. This shows that Ford is aware of the issue but the question remains what do the rest of us do. Do we chase cracks forever? Can we purchase that newer bracket to weld in? Will just fixing the cracks as they show up work?

In the meantime, I hope this helps ya'll and serves as a reminder to check those welds! Worst case scenario, you dont catch this and your upper arms come detached while wheeling or on the freeway.

See the below pics.

My Bronco before repair

My bronco after repair

21 stock Sasquatch (note rust at arrow)

23 Bronco with boxed bracket

21 Bronco with open bracket

My second crack that I found after fixing first one

***edit*** got some great feedback from y’all. It appears that random 21Broncos have the open style prone to cracking. As of now there is no rhyme or reason which ones get it that I can tell! The 22’s and up all seem boxed. There is No date cutoff as some early Broncos have the box and some late 21’s do not. The cracks seem to start with rust forming in the welds which someone mentioned could be a sign of poor welds. As of right now there is no solution but the recommendation is to go to Ford if cracks form and report it. If you have the open design and no cracks, just watch it. I have not seen cracks on a stock Bronco but I have seen the rust showing

I must have been one of the lucky ones. My 2021 was built in the last week of that model year.

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