I'm really embarrassed and at this point have no shame. I feel like I've been asking a lot of questions as of late but this is something entirely new.

For context: I was driving in Central Oregon going shooting and getting ready for hunting season with a co-worker in the 2000 automatic D2. I took her to a spot very uphill and low gearing isn't a necessity but you can feel the difference it makes. Anyway, I have to reverse at one point, and while reversing in low-gears, the engine revs up uncontrolled and when I attempted to pop into neutral at 4,000 RPM in low there was a major thud and the engine died.
Upon inspection, my air intake had popped off the plenum and unmetered air was being sucked in which accounted for the engine dying and high revs. Fixing this allowed me start the engine but for the first 30 seconds or so it didn't matter what gear I was in, nothing happened. I managed to shift back into high gear and drive down the hill in drive after another large thud, shoot for 4 hours, patch my tire and drive home.

My questions and the lasting problem:
I recently replaced my rear driveshaft with 4 bolt conversion and the front shaft is a Lucky 8 greasable that I grease every month-every 3 months. I drove home fine (60 miles), via offroad trail and highway but now I have a noticeable but not currently detrimental vibration around 30-50mph and a severe oil and transmission fluid leak.

I can confirm the leaks later since my work week starts tomorrow AM but what do you suppose I need to replace? This is my fourth Disco and the first one that I feel like I can't catch a break with but I love it dearly.

Edit: Forgot to mention, when I got home I went back to low gears and tried everything and it all works fine, just a vibration at 30-50mph when it used to only be from 40-45mph and a severe oil and tranny leak, moreso the tranny by the looks of it.

 

Do you have the PCV mod done? I am wondering if you have popped a seal due to high crankcase pressure.

 

The PCV mod looks like it will solve some quirks but I'm thinking as far as the intake popping off, it was likely me not tightening the hose clamp tight enough.

It seems I need to replace my transmission oil pan gasket so I'll be doing that this weekend and I'll do the PCV mod at the same time. Then on to figure out the vibration once and for all.