Rear axle breather puking ...
I had problems with oil coming out of the breather tube during long duration highway trips in my E350 4x4 (SMB conversion, using a full floating Dana 60 rear). The only 'problem', as far as I could tell, was the smelly oil blowing everywhere. Extending the breather hose didn't do anything. Putting on different jiggle caps or a K+N at the end of the breather hose didn't do anything (i.e., it still puked oil).
In the end, I found that is was ever so slightly overfilled, every time I swapped out the oil (I was just following the recommended quantity), so it would puke - at higher temps. I also switched to a Trail Gear Creeper Breather, which is an expandable yet closed axle breather system. They are not expensive. It doesn't let condensation out, but I have not seen water in the oil when drained.
I, too, look forward to the Banks data.
2010 Ford EB E350 4x4 6.0L with SMB Penthouse