broken rear long side axle shaft

arnott1t

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Re geared my wagon yesterday and installed and ARB front and aussie rear locker. Set the gears up with Nitro 4.56 gears instead of factory 3.7's. Backlash set yo .007" and pattern looked really good. Aussie went in flawlessly with all the right clearances. Filled it with fluid and drove off. Sounded good and felt good. Did a hard start on wet pavement and bang..... Still waiting to get the truck home but we pulled the axle out the side last night and it has a great torsion failue near the splines. Could I have messed something up? Or is it just the added torque? 35" SSR with a turbo'd 2H. Never had breakage issues before..... Arre poly's worth the $$. doesn't seem like this is a common problem. Any one have a long side rear axle shaft?
 
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My stocker axles lasted thru wide 38's with an aussie in the back. I am running an auto so I know that helps absorb some of the shock loading from low rpm diesel torque. Were you slightly turning? Tire pressure the same on both sides? Sounds like previous damage/weakening finally letting go.
 

arnott1t

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didn't look for bends but I can now. Everything came apart nicely. Not sure what else it could have been. I'll try and get some pic of the failure. It looks like a perfect torsion failure. at a 45* angle. I have a metalurgy pal coming by to take a look at it too. Maybe he'll see something. It almost, I'm reaching here, looks like there was a previous crack. on the face of the break there is a band of smooth break about a 1/4" wide around the outside while the center is very rough. I think I recall from some engineering courses this could be caused by fatigue fracture on the outside and brittle fracture in the center. The fatigue didn't have the lines on it though like others I've seen so it may just be from the heat treating process.

I'll likely just replace with a stocker and go from there.
 

arnott1t

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So it looks like its an old crack that finally gave up. My buddy confirmed my suspicions. Pics to follow later.....
 

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