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

[ajordan1975]

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?

Honestly..... you can polish it out, but no real need... I've seen and had far worse gouging in the bells and they've been fine. If the axle seal area got messed up that's when i would worry,

 

[ajordan1975]

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.

I was there!

 

[ajordan1975]

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.

This is one of the best reasons for having a PT case.

 

[Devil's Slide Doug]

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

You need to have spare parts (at least on rock crawling trails, especially if you drive to the trail) but at what point to do you add enough weight in spare parts that your truck is so heavy is starts breaking more stuff?

 

[suzuguru]

It takes a lot of wheeling to know what to carry and what to leave at home. It's a delicate balance. You'll never get it perfect, but after several years of off-roading, you pretty much know what you need. If you have an off-roading partner, you can each carry different things that you can share if needed.