Driveshaft/TC problem?

ok, now I'm frustrated. When I drive, every once in awhile I hear a pining from my driveshaft. I removed the DS, new u-joints, etc. When I put it back in, it had a little play (like it's supposed to), but after I drove it about 100yds, it starts pining again & the driveline is completely spooled up - it won't budge when the jeep is stopped.

So my question is - is this a driveline problem or a TC problem, or a rear dif problem? I've got a stock NP231, but lifted the jeep and got a new driveline (extended about 1") to account for the lift.

Ack! Any ideas/help is appreciated. I'd take it to a 4wd shop, but then I'd hafta drive it there & that's not gonna happen...