My 96 Yukon wont move

hello all....
I have a 1996 Gmc Yukon 5.7l 4wd push botton. Yesterday while driving on the freeway at 65 the trucked jerked a couple of times and threw a po1870 code. As i was limping it to get home driving up a hill i heard a clunk from under my seat and I lost all power. As i was sitting in the middle of this hill I let off the brakes to try and coast off to the side of the road and it would not move, like the brake was on but it wasnt. I finally dragged it on to a trailer with the help of a trusty winch. I got it home crawled underneath and had to disconnect the driveline to get it off of the trailer. With the rear axle off the ground I could spin the tires easily so the rear end and the brakes are seeming to be ok. I noticed that the underneath was coated with fluid but only from the transfer case back. There is a module on the bottom of the tranfer case that is soaked. I cannot turn the driveline in any gear or neutral. it shifts from 2wd-4wd fine and back again but will not drive in any gear. Although in reverse it feels like it is trying to grab but nothing happens. Please help any advice would be helpful.

Could be the transfer case is locked up, can you turn the ft drive shaft?