clunking 4x4???

Hey, I'm an owner of a 1989 cherokee lareado, recently I've been hearing a rather loud clunk from the front end of my jeep when four wheel drive is engaged, it usually doesn't happen untill i'm at least in third gear or so, and it feels like it's gonna rip the front end off. I've recently noticed some lines hanging by the transmission, they almost look like breather lines, or something. this is my first jeep and pretty much the first 4x4 I've ever worked on. Is there a diagram showing these lines so I can put them back where they belong??? Thanks.