It sounds to me like what a dry bearing would sound like... Kinda like a squeak-rattle combo
After crawling under the Jeep for a second time, I'm leaning towards U-joints.
The diff cover is on tight, but I don't have the right tool to pull the fill plug to check the level.
I wiped the bottom lip of the diff cover and will re-check on Monday.
There is no leakage at the pinion seal, nor is there play *at* the pinion as far as I can tell.
There IS play at the slip joint and somewhere at the cardan joint end. It FEELS like about a millimeter or so.
At the very least it's visible and causes a thunk when moving the shaft laterally.
I'm going to try to get the shaft pulled on Monday, and if it's the source of the noise I'll get it rebuilt.
Which begs a question:
How much can the slip joint be extended and still be considered within tolerance?
At my current 7" of lift, there is about a 2" gap between each side of the shaft (with the Jeep on the ground).
By the way, it is the stock front shaft