Drive-train/transfer case problem

Information:
I have a 2001 WJ with 180,000 miles on it (second owner). Fluid changes have been regular. Has a 4" lift with E-Locker in the front as well some other stuff that I don't think is relevant.

Backstory:
About 10 days ago I went off-roading in Northern Colorado and blew my rear shock. Replaced both rear shocks with exact same Bilstein 5100s. Everything seems to be going fine, but then take a 300ish mile trip to Vail barely making it home.

Issue/Diagnosis:
On return (after 140ish miles) to Vail I noticed, every once in awhile, that my drivetrain would lock up, not pulling left or right, but just locking up and preventing movement. Eventually the lock ups got more frequent, louder, and lock ups lasted longer. (All this time I'm only in 2WD, at this point I haven't put it in 4WD Low or Hi.

1. Checked U-Joints, both in the front and rear driveshaft, everything looked good. However, when moving the front drive shaft there was a slight rotation play, but no other wiggle in another direction.
2. A few months ago I replaced my passenger side CV Joint, Axle shaft, and ball joints; so I decided to check the driver side hub assembly, but nothing seemed off including the hub bearing.
3. After hub bearing was checked, I removed the CV Joint, connected to the differential, to find some dirt in the spline connecting to the diff, but I couldn't see any metal shavings.

After putting the hub assembly back on I tried to drive it again, in 2WD, and as soon as I hit 10-20mph the sound came back and the drive-train froze and I was frozen in the street in Drive. I had then switched to 4WD Part-Time and was able to return home but the sound and locking was still there.

After my tests, I think the diagnosis is a bad transfer case, thoughts?
-NP242 Transfer Case
-Double Cardan Front Drive Shaft
-When the car locked up in my neighborhood, I could hear spinning as I pushed the gas but no movement at all until I switch into 4WD Part Time
-I raised each front tire independently and rotated them, and couldn't hear an audible clunk from the front differential. (Maybe I just couldn't spin the wheel fast enough)