The X5 lives again! Huge thanks to jcorreanyc for selling me a 4.6is transfer case (apparently the 4.6 has a special LWX-500 transfer case) and shipping it all the way out from NYC. That was one heavy sucker!
The full writeup is coming later today once I can get everything off my DSLR, but let's just say it was quite the job! The transfer case is quite heavy when you have a foot and a half of clearance under the vehicle and the exhaust is quite fun to maneuver into place.
I replaced the transfer case, replaced the chain inside the transfer case, and replaced the front driveshaft with a brand new 1" extended one from Cobra Transmission. Fresh Dextron (5?) fluid inside the transfer case.
It's still quite filthy from sitting outside for the better part of 4 months, but it drives great. No check engine lights, no warning lights, and the drivetrain is super smooth. I took it on a shakedown at like 2:30am last night and everything went quite well. The engine fired right up and initially had a lifter tick from sitting for so long, but after a drive it sounded pretty good.
I drove it to work today and it was awesome. I forget how quick 4.6's feel, even though they're not all that quick on paper.
I documented the first part of this repair job in this video on my YouTube channel (shameless self-promotion):
https://www.youtube.com/watch?v=QBy1HcVHOrM