Thanks for the replies.
Got a clanking that starts above 20 mph or so. The local Tunex guys couldn't diagnose it. I suspect a U joint has gone bad in the front driveshaft, I'm gonna take that out myself this afternoon to see if that's it. If that isn't it, that kinda leaves things like the diffs, transfer case and transmission, all of which are beyond my mechanical knowledge/skills to deal with. I'm certainly open to suggestions.
This is on a '00 WJ with a 2" Teraflex BB. Driveshaft is the later version with the double Cardan joint at the TC end instead of the Rzeppa CV.