Part of the problem is that the housings on the JK are about 6 inches wider than previous models, the C's are correspondingly taller, and the JK's themselves are a lot heavier. This makes the C's and housing tubes more prone to bending, even on bone stock jk's that have never been offroad. And then you get into the suspect metallurgy that may be causing some of these housings to shatter at the passenger side ca mounts.
(note that the d30 front and the d44 front on the rubi are basically the same housing. Same outer diameter and wall thickness, same c's. The difference is that the center section on the 44 is larger to fit the 44 gearset).

No modifications are mandatory, but adding gussets to strengthen the weak C's, and sleeves to strengthen the tubes are not a bad idea.

 

That's just poor engineering, or bean-counting. I've been in executive management too long - that's just inexcusable. Any attorney worth their sheep skin should/could prove that Jeep wants you to buy these rigs and modify them.

Ok, Friday night chill time...

 

To the OP, I've seen a lot of reports of people with D30's running 37's and even one on 40's with stock axles and not having breakage after multiple seasons. But..... it depends on how you use your rig. Those people are not driving aggressively and are probably using 4wd only occasionaly, having 40's more for style than off-road performance.

I just got a new Rubi and with less than 500 miles on the odometer, I've already had it stuck twice and have done some body damage. The first time I was trying to climb a steep hill with rocks and one front tire slid off of a rock and set the differential down on a boulder. Then the rear tires spun and the rear end went side ways, placing my quarter panel directly in front of a 3 foot high boulder. I couldnt back up. The only way was forward with lots of throttle and axle hop to push the front diff off the rock while climbing a steep grade. The second time I got stuck was in mud/water that was half way up the door panels and I had to climb out the window to prevent flooding the cabin when I went to get hooked up for a tow. Needless to say I was using lots of wheelspin, forward and backwards before I gave up and decided to go for a swim.

If you treat a D30 with 35" tires on it like that, it might not even last a single day. I actively search out the most challenging things that I think I can get away with, without bodily injury. So if you like challenges, stay with a smaller tire to prevent eating up the diff.