Re: WK rolling ball bearing noise
some "play" is normal in the front driveshaft.
Honestly, this is something that will be nearly impossible to isolate without having the vehicle but I will say I have never heard any complaints like yours. Your complaint sounds exactly as you have concluded, something rolling until it hits something... there is nothing in the transfercase that will make this noise, nothing in the transmission or engine either.
It could be almost anything because the noise you describe doesnt sound like a car failure but a loose item. From there you just need to isolate the noise better (as I understand you already know). has there been any big work done (engine tear down, exhaust replacement? for example I just did the head gaskets on my parents subaru last week, I was removing a ground bolt and what are the odds, it dropped down and clanked down in to the exhaust I had unbolted from the motor. I did fish it out but an example of a noise that I caused that would make a similar noise to your complaint.
Good luck man!
2005 Jeep Grand Cherokee - Gone but not forgotten!