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arse_sidewards said:
JR4X have you taken a sawzall to the frame yet? :flipoff2:
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Not a sawzall to the frame. Did zip disc on the frame. Sawzall on the body though. Mentioned it in my build thread. Saw blades and drill bits won’t touch whatever the roll cage and windshield frame are made of. Only abrasives will cut it. The frame is 3/16” thick and in some places it’s double layered 3/16” thick.
 
Just scrolled up and saw the context to the question. Myself and Atteberry didn’t use the factory upper link placement because the upper links are maybe 12” inches long. Loren and Vaughn’s uses the factory upper pivot point thiugh
 
I just sent Mitch a message, and Bronc Buster as well about working towards coming up with a bracing solution.

Not sure how practical it would be if they have fixed this already, but mine is a 2020 iirc so it might have the issue as well.
 
Talon2006 said:
I just sent Mitch a message, and Bronc Buster as well about working towards coming up with a bracing solution.

Not sure how practical it would be if they have fixed this already, but mine is a 2020 iirc so it might have the issue as well.
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Bronc Buster? Why support a guy that thinks it’s ok to ruin iconic trails and not fix it? Claims he will fix it next year?
Back to the top….
 
Talon2006 said:
I just sent Mitch a message, and Bronc Buster as well about working towards coming up with a bracing solution.

Not sure how practical it would be if they have fixed this already, but mine is a 2020 iirc so it might have the issue as well.
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I have a fab guy also working on a fix. I’ve documented multiple modified broncos and 2 stock broncos with the issue now. All are occurring to 21 Broncos. It seems a small batch of frames (estimating several hundred) were made in early 2021 with the open design bracket (pictured). These were randomly added to 21 Broncos. Then the design changed and all Broncos since have gotten the boxed brackets with no known issues. Bottom line is that if you’re a 21 with the open design. Keep an eye on it. If you wheel hard or are modified you’re likely to crack. Bronco6g has an extensive thread on the topic that is pages long. Too much to go over. Essentially in 21, it was completely random if you got the open, weaker design or stronger, boxed design. Luck of the draw based on the feedback and research done so far. The early run of frames were scattered throughout the lineup.
 

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Talon2006 said:
What trail did he destroy?
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Rubicon, Mitch was broke down and bb decided it was a grand idea to winch a rock out of the way and didn’t put it back. Called him out numerous times and he came back with the response “I’ll put it back next year.”
 
SLOWPOKE693 said:
When do we get to add weak front differential mounting brackets to the list? :laughing:

JR4X
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I’ll get pictures soon. This is the second time I’ve had issues with that particular area. Have had issues with the diff side of the mount before. Fixed that and now tore the bracket off the frame.
 
JR4X said:
I’ll get pictures soon. This is the second time I’ve had issues with that particular area. Have had issues with the diff side of the mount before. Fixed that and now tore the bracket off the frame.
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Do you think torque from the portal reduction working in reverse when bumping a ledge or similar situation is tearing the brackets off or something else?
 
SLOWPOKE693 said:
Do you think torque from the portal reduction working in reverse when bumping a ledge or similar situation is tearing the brackets off or something else?
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I do think that. When being powered the portals are a gear reduction and take strain off the diff. When being spun by the tires it increases the speed and force on the diff. Something about the portals makes it where when you do a panic brake coming into a corner or a whoop is really hard on the diff.

I can feel it in my feet. In Montana the first time it broke the factory hardware holding the pinion support. I was coming into a corner too hot so I got on the brakes as hard as I could. Both felt and heard the snap. This time, coming into big whoops way too hot. Did a nose dive hard on the brakes, felt and heard the snap. Atteberry is having the same issue but theirs breaks the R&P.
 
JR4X said:
I do think that. When being powered the portals are a gear reduction and take strain off the diff. When being spun by the tires it increases the speed and force on the diff. Something about the portals makes it where when you do a panic brake coming into a corner or a whoop is really hard on the diff.
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Imagine if the drive shaft going out the pinion was fixed and the axle coming out of the diff spun. The housing would have to spin to let the axle spin.

Because the whole rest of the upstream drive-train can't change speed instantly there's some force like this being applied to the diff when you stomp the brakes or hit a ledge.

The speed increase from the portal ratio is trying to make the drivetrain change speed faster for a given wheel speed change so the housing is getting hit harder.

Is the diff bushing mounted? Can you switch to a harder rubber or a bigger bushing so that the force doesn't blow right through it?
 
arse_sidewards said:
Imagine if the drive shaft going out the pinion was fixed and the axle coming out of the diff spun. The housing would have to spin to let the axle spin.

Because the whole rest of the upstream drive-train can't change speed instantly there's some force like this being applied to the diff when you stomp the brakes or hit a ledge.

The speed increase from the portal ratio is trying to make the drivetrain change speed faster for a given wheel speed change so the housing is getting hit harder.

Is the diff bushing mounted? Can you switch to a harder rubber or a bigger bushing so that the force doesn't blow right through it?
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It is bushed and has a dog bone 🦴 like a lower strut. On the V6 broncos you can’t get the diff in and out without taking this thing off. So the fun havers have had problems breaking the bolts after assembly. On my little 4 cylinder I don’t have to unbolt that to get it in or out. But it’s broken the bolts that hold the dog bone and the mount the bone is bolted to. First two pics are a fun haver diff from a couple years ago. The frame pic if you zoom in you can see the cradle diff mount when it was still new.

IMG_3264.jpeg
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IMG_3152.jpeg
 
arse_sidewards said:
Imagine if the drive shaft going out the pinion was fixed and the axle coming out of the diff spun. The housing would have to spin to let the axle spin.

Because the whole rest of the upstream drive-train can't change speed instantly there's some force like this being applied to the diff when you stomp the brakes or hit a ledge.

The speed increase from the portal ratio is trying to make the drivetrain change speed faster for a given wheel speed change so the housing is getting hit harder.
Click to expand...

So my brother and I are disagreeing slightly on this. Brother thinks it’s just breaking from use and that slamming on the brakes has nothing to do with it because the brakes are outboard of the portals.

But he’s not raced it yet and I swear I can feel something weird in the front end when I jam on the binders. It makes the transfer case whine when I slam on the brakes but it doesn’t whine when I’m on the gas. Think it’s possible having portals in the front and not in the rear does something mechanically mismatched when I lock up the brakes?
 
JR4X said:
But he’s not raced it yet and I swear I can feel something weird in the front end when I jam on the binders. It makes the transfer case whine when I slam on the brakes but it doesn’t whine when I’m on the gas.
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Well you have a lot less torque with the skinny pedal than you do with the wide one....

JR4X said:
Think it’s possible having portals in the front and not in the rear does something mechanically mismatched when I lock up the brakes?
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So long as there's the same amount of total gear reduction between your brake pad and the pinion yoke I don't think this can be the case.

Which, bringing this back around, makes me think that the effect of the portals on the drive shaft and such is no more than what an equivalent ring and pinion would get you. So in light of that I want to reconsider my comment.

The drive shaft and transfer case can't tell the difference between a 10:1 ring and pinion vs a 5:1 with some 2:1 portals or planetary ends.

It also can't tell the difference between 10:1 at one end and 5:1 X 2:1 at the other.

But that's theory. You're breaking shit in reality.

Someone smarter than me needs to think about the gearbox mounting forces at play here. You've got two separate gearboxes up front and I think that's making it more complex than it would be if you had a portal solid axle because the forces that keep them from spinning relative to each other have to go through the mounts and the suspension and whatnot vs straight down a tube.

My gut says that since this is an issue of speed change and inertia in the rest of the rotating mass of the drivetrain.

Can you get an Oshkosh sponsorship? They can probably have the relevant experience to help you sort it out. :laughing:
 
Also, isn't this exactly the kind of thing your OEM rep should be helping with?

If it's failing when you race it's going to fail when other people bolt portals on and floor the brake pedal the street where they will have far more traction available to break shit with.
 
arse_sidewards said:
The drive shaft and transfer case can't tell the difference between a 10:1 ring and pinion vs a 5:1 with some 2:1 portals or planetary ends.

It also can't tell the difference between 10:1 at one end and 5:1 X 2:1 at the other.
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It may be an issue of 10:1 at one end and 5:1x2.01:1. The diff may not be designed for the binding
 
Those mounts are pretty close to the rotational centerline, if I am looking at it correctly. What about some sort of girdle mount around it closer to the pinion?
 
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