I have never heard of the "dreaded Bronco lean", or axle tubes slipping in the housing on a D30. The AMC model 20 leaks on my heep there though.
Yeah, a common issue on the AMC 20 as well. And that was all stamped steel housing, correct? Been awhile since I was dealing with those.
Never had to deal with a leaky one, but heard of them many times. Porous metal or something? I think both Dana and Ford had that issue with rear end housings as well sometimes.
If a 30 leaks at the interface between the cast center housing and the tube, it's a good chance the tube could spin too, given the right amount of "inspiration" to do so.
The good news is that in most minor cases a simple application of some silicone will stop the leaking. Won't cure the loose tube, but at least the driveway stays clean for awhile.
If you're not going to be off-roading, this loose fit will probably never cause any dire issues. But it will twist back and forth even under normal cornering and bumping about, so if it is seen to be much of an issue it's easy enough right on the vehicle to have someone put a few welds where they count.
It doesn't come up here that often anymore. Maybe you won't run into it either.
Paul