As far as the diff breather caps go, they have had that design through all the runners I believe. My 1st gen sat through 3 high tides on the columbia river, the highest tide went 3/4 up the windshield. I drained about 7 gallons of milky fluid out of my engine, tranny, and transfercase, but none made it in my diffs. With driving in water, I found a little bit will make it in with alot of water crossings, but if you change your diff fluids every other oil change, it's fine. I had a 90 2dr runner that got stuck in a mud hole, I made it out, but muddy water covered my hood and was a few inches below my door windows, and my oil, air filter, interior was fine, and I spent a couple minutes in it trying to get out. 2nd generation on up has a really nice water baffle design on their intake, so you really have to submerge it for a bit to suck some in.