Birf inner race blew up - how and what next? (1 Viewer)

[96TrailSurfer]

Wheeling last weekend, I was crawling down steep rocky a shaly decent with several turns, got stuck against a rock and was unable to turn (wheel would simply not turn), freed myself, heard a small ping while making the turn, and, as turned onto a flat ground I heard a very loud PING.... and shortly thereafter discovered that I had no power to the front wheels, and thus a blown axle.

Got home, took everything apart, and found that the inner race of the LH birf had blown up, specficaly, the inner (diff size) ring. Below is a pic of what it looks like glued together with crazy glue.

I now have RCV axles on order and am in the process of rebuilding both side's knuckle, including replacing all seals and bearings.

I have two questions:

First is why did this happen? The way that I understand a birfield joint works is that the inner shaft axleshaft transfers power to the star, the star to the 6 bearings, the bearings to the bell, and the bell is part of the outer axleshaft which rotates inside the spindle and transfers power to teh drive flange. The race (cage) of holds the star and the 6 bearings together but I thought it is not a power transfer component.
(this video seems to confirm that )

So why would it explode? I'd like to understand it so I can prevent it in the future. My best guess so far is that the knuckle seals had been leaking for a while and the bell was low on grease .... or just an old component?

Second, when the race exploded and I drove like this, the debris made some gouges inside the bell of the axle housing. Nothing too deep, but to me looks like something I should polish out. So my question is should I be more worried about this, and what's the best way to polish it out? I was thinking some kind of a wire wheel or brush bit for a dremel?

Final question, should I be polishing the outside of the axle housing bell where the knuckle moves about it?

 

[mudgudgeon]

Why did it happen?
Everything has its limits.

Sounds very much like a situation I was in when I've shattered a birfs in the past.
Wheels turned to full lock, and then putting power to it when it's at its maximum functional range of movement!
In that situation, the transfer of power through the birf is not a direct line. The more its turned, the more load is exerted on the ring that broke
It's like using a universal joint with your socket sets. Trying to loosen a bolt that's badly out of position, you can watch the universal joint twist and contort itself. I've busted a couple of these over the years. You can see the forces in action.

Avoid putting power to the wheels when you have them turned at full lock, and jammed in a corner.
Sometimes it's unavoidable, and you roll the dice.

 

[suzuguru]

I'm no expert on the matter, but the damage to the bell on your axle housing is significant. At a minimum, you're going to need to polish that out.

 

[manofthewoods]

Why did it happen?
Everything has its limits.

Sounds very much like a situation I was in when I've shattered a birfs in the past.
Wheels turned to full lock, and then putting power to it when it's at its maximum functional range of movement!
In that situation, the transfer of power through the birf is not a direct line. The more its turned, the more load is exerted on the ring that broke
It's like using a universal joint with your socket sets. Trying to loosen a bolt that's badly out of position, you can watch the universal joint twist and contort itself. I've busted a couple of these over the years. You can see the forces in action.

Avoid putting power to the wheels when you have them turned at full lock, and jammed in a corner.
Sometimes it's unavoidable, and you roll the dice.

Excellent response above.
In simpleton terms (I'm a simpleton)...
Stress on any CV joint increases significantly as the degrees away from straight line increase. If/when possible apply as little torque when turning as possible, especially in tight turns.

As a sidebar, every one should go give your Birfs a hug. They do a thankless job..

 

[96TrailSurfer]

I'm no expert on the matter, but the damage to the bell on your axle housing is significant. At a minimum, you're going to need to polish that out.

I intend to. My question is how - what's the best tool / process?

 

[96TrailSurfer]

Why did it happen?
Everything has its limits.

Sounds very much like a situation I was in when I've shattered a birfs in the past.
Wheels turned to full lock, and then putting power to it when it's at its maximum functional range of movement!
In that situation, the transfer of power through the birf is not a direct line. The more its turned, the more load is exerted on the ring that broke
It's like using a universal joint with your socket sets. Trying to loosen a bolt that's badly out of position, you can watch the universal joint twist and contort itself. I've busted a couple of these over the years. You can see the forces in action.

Avoid putting power to the wheels when you have them turned at full lock, and jammed in a corner.
Sometimes it's unavoidable, and you roll the dice.

Advice is solid, and I think I understand the forces better... at extreme angles, the balls are pushing not only against the star and groves in the bell, but also against the race that keeps them together I think at the corners where ring meets the side "side walls". Add component fatigue and old and/or insufficient grease, and maybe debris, and boom

Would you polish out the gouges in axle cup housing and if so, what would you use?

 

[mudgudgeon]

I intend to. My question is how - what's the best tool / process?

Most of it really doesn't matter. I've had mine looking worse than that.

Just deburr so you don't tear a hunk out of your finger next time you're in there scooping out birf soup.

Use a flap wheel in a drill. Stay clear of any machined faces bearings fit to.

Also, as a side note. If you smash a birf, stop and strip all the shrapnel out as soon as practical, and before driving at any speed.
Shrapnel can jam up and lock a hub up. Not something you want to happen on the interstate on the way home

 

[96TrailSurfer]

Also, as a side note. If you smash a birf, stop and strip all the shrapnel out as soon as practical, and before driving at any speed.
Shrapnel can jam up and lock a hub up. Not something you want to happen on the interstate on the way home

100%
My first time with this issue and I (naively) thought I blew the shaft or the splines, didn't even think that this was the issue and there would be debris. Drove home 350 km on it. I am lucky af nothing bad happened.

 

[mudgudgeon]

 

[mudgudgeon]

100%
My first time with this issue and I (naively) thought I blew the shaft or the splines, didn't even think that this was the issue and there would be debris. Drove home 350 km on it. I am lucky af nothing bad happened.

I think odds of them not jamming up are probably in your favour, but could be nasty, so not worth the risk.
I had one jam up completely almost immediately after it happened on the trail. Wasn't even clear off the trail obstacle.
Lockers and turbo diesel goodness got me to a spot level enough to strip the hub

 

[suzuguru]

I intend to. My question is how - what's the best tool / process?

I've never had to do it, so to be honest, I don't know. I would probably start with some fairly fine grit sandpaper. There's probably a better method. I tend to try the least invasive method first. Looks like others have also chimed in with good advice.

 

[CharlieS]

The flap disk is a quick, easy and affordable option.

I find a die grinder with 3m Roloc disks does a good job of surface conditioning albeit more expensively.

You can get all kinds of different abrasive disks. I'm sure there are knockoff products online too. Not sure I'd buy one for just this project, but I find them generally useful to have around the shop. An air powered one would be cheap, assuming you have a compressor. I have a Milwaukee M12 right angle cordless die grinder that I use regularly.

 

[MUDZLLA]

Was your front diff locked at the time? Never had a birfield go when it was unlocked. Now I keep the front unlocked when wheeling and avoid jamming the wheels to one side under power. Using the winch is easier than rebuilding a broken birf.

 

[rc51kid]

Most of it really doesn't matter. I've had mine looking worse than that.

Just deburr so you don't tear a hunk out of your finger next time you're in there scooping out birf soup.

Use a flap wheel in a drill. Stay clear of any machined faces bearings fit to.

Also, as a side note. If you smash a birf, stop and strip all the shrapnel out as soon as practical, and before driving at any speed.
Shrapnel can jam up and lock a hub up. Not something you want to happen on the interstate on the way home

Correct me if i am wrong. But this was one of my thoughts when i went to part time. I figured that if i broke one, it gave me the option to run rwd and all the front drive system could be disengaged.

At the end of the day, for my current use i wish i had kept the full time. But that is another conversation.

 

[rc51kid]

Wheeling last weekend, I was crawling down steep rocky a shaly decent with several turns, got stuck against a rock and was unable to turn (wheel would simply not turn), freed myself, heard a small ping while making the turn, and, as turned onto a flat ground I heard a very loud PING.... and shortly thereafter discovered that I had no power to the front wheels, and thus a blown axle.

Got home, took everything apart, and found that the inner race of the LH birf had blown up, specficaly, the inner (diff size) ring. Below is a pic of what it looks like glued together with crazy glue.
View attachment 3640289View attachment 3640291

I now have RCV axles on order and am in the process of rebuilding both side's knuckle, including replacing all seals and bearings.

I have two questions:

First is why did this happen? The way that I understand a birfield joint works is that the inner shaft axleshaft transfers power to the star, the star to the 6 bearings, the bearings to the bell, and the bell is part of the outer axleshaft which rotates inside the spindle and transfers power to teh drive flange. The race (cage) of holds the star and the 6 bearings together but I thought it is not a power transfer component.
(this video seems to confirm that )

So why would it explode? I'd like to understand it so I can prevent it in the future. My best guess so far is that the knuckle seals had been leaking for a while and the bell was low on grease .... or just an old component?

Second, when the race exploded and I drove like this, the debris made some gouges inside the bell of the axle housing. Nothing too deep, but to me looks like something I should polish out. So my question is should I be more worried about this, and what's the best way to polish it out? I was thinking some kind of a wire wheel or brush bit for a dremel?
View attachment 3640297
Final question, should I be polishing the outside of the axle housing bell where the knuckle moves about it?

I think you already got a good answer from more knowledgeable people than me. But i think the machined bearing surfaces and seal surfaces are critical. The rest is kind of a structural grease pocket.

 

[mudgudgeon]

Correct me if i am wrong. But this was one of my thoughts when i went to part time. I figured that if i broke one, it gave me the option to run rwd and all the front drive system could be disengaged.

At the end of the day, for my current use i wish i had kept the full time. But that is another conversation.

In reference to a busted birf?
When mine broke, the shrapnel jammed to the point where it instantly locked the front wheel on that side. Shrapnel busted more, and it kept rolling. Could be ugly on the highway.

If you had free wheeling hubs disengaged, maybe that would eliminate this scenario?

 

[rc51kid]

In reference to a busted birf?
When mine broke, the shrapnel jammed to the point where it instantly locked the front wheel on that side. Shrapnel busted more, and it kept rolling. Could be ugly on the highway.

If you had free wheeling hubs disengaged, maybe that would eliminate this scenario?

It has been a long time since i thought about it and i could be wrong. But yes, my understanding is that with the hubs unlocked and a true partime system everything in the birfield, front drive shafts and front diff are completely stationery driving down the road. But like i said, i could be wrong.

 

[Devil's Slide Doug]

My son was driving my 80 on the Rubicon trail and got stuck in a hole/rockpile. He proceeded to crank the wheels all the way over and engage the front locker. Bam! Broke the long inner axle, cracked the inner race and outer bell and shattered the cage.The wheel jammed and would not turn so I twisted/unlocked the hub dial and we drove a very short distance to a flat spot to replace the birfield and axle without blocking the trail. He learned how to swap a birf on the trail. I learned that although I had a spare birf, I was lacking a long side shaft but was lucky to borrow someones spare. RCV's are on my work bench waiting to be installed and I will have a full set of trail spares after installing them.

 

[ajax1]

If the truck is jammed and wo t steer do not force it, that is when it will break, you might have bent your steering shaft on the box, pretty common, you can also break the knuckle or steering arms off. With damage in the axle housing I would clean it up good, take any sharper edges out, get it as smooth as possible, think be okay if you polish that out

 

[suzuguru]

My son was driving my 80 on the Rubicon trail and got stuck in a hole/rockpile. He proceeded to crank the wheels all the way over and engage the front locker. Bam! Broke the long inner axle, cracked the inner race and outer bell and shattered the cage.The wheel jammed and would not turn so I twisted/unlocked the hub dial and we drove a very short distance to a flat spot to replace the birfield and axle without blocking the trail. He learned how to swap a birf on the trail. I learned that although I had a spare birf, I was lacking a long side shaft but was lucky to borrow someones spare. RCV's are on my work bench waiting to be installed and I will have a full set of trail spares after installing them.

It's a pain to carry around all those spare parts, but it's great to have them when you need them.