I've got an aussie and 5.13's in mine and I've broken the short side U-joint twice. Of course I wheel the piss out of mine.

 

Possibly could be from poor installation but the gears have been on since about 16,000. And sounded good all the way up till they broke.

 

I had the u-joint cap walk off on my passenger side on the Rubicon (the trail) and take out the joint with it. Three-wheel drive on that trail is no fun, and the other u-joint popped a short time later (that one was more my fault). Being in 2wd from that point on, I was hammering the crap out of it to make it through the second half of the trail. As a result, I wound up severely tweaking the passenger side lower control arm mount.

Note that all the stuff that failed is identical between the JK D44 and 30, so I think it was mostly bad luck that the joint failed in the first place. I'm running 5.13's, an ARB locker, and 35's, so the part that you would think would be most susceptible to failure is the ring and pinion, but I've been fine there.

Oh yeah and I took the opportunity to build it up a little bit when I fixed it:

 

15,000 miles on lift and 35's and no problems. I did have the Pass side front U joint go but I noticed that when I was putting on the lift and 35's and replaced it then. Since then no problems.

Recently I put on EVO C2 and LCA brackets. I have had 11 good wheeling trips before the gussets and 3 after and no problems so far.

 

60k on mine and I replaced the 32" tires in the first 5k. Went 33" for 20k and since have had 35" tires on steel rims. I have 4.88 gears since 10k.

The biggest issue I had is I replaced the u joint on the drivers side as it had a little play last month. Other than that I'm surprised it's done so well.

 

I went to 35s and did evo gussets at 4k miles, I now have 17k and just put my 5.13s in today. It has been wheeled hard several times with no problems.

 

35x12.50R15 MT/R Kevlar. Open and snow wheeling. Busted u-joint took out the ears which in turn took out my passenger side ball joints.

 

dude, are you running a fever or something? only 35s?

WOOHOO I GOT BIGGER TIRES THAN YOUUUUUOU!!

37's here , so far no damage from the mods. 5.13 gears and locked. only damage was cap popping off u-joint which led to replacing outer shaft and ujoint, but those little c-clips are bad for coming off.