99 xj with np242

Problem: put it in 4wd part time,full time, and 4Lo Does it in all of those but never in 2wd I'm getting a really loud clunking/skipping what seems to be coming from the transfer case with a little gas or a lot it will do it....any thoughts I'm thinking transfer case chain? All fluid is good I also am curious if it could be the front diff which is a D30 haven't had a chance to crack the cover open would I mostly be looking for anything out of the ordinary or the most obvious of metal chunks and shavings!?

Any help would be greatly appreciated guys! We just got covered with snow so no 4wd is a major bummer! :-)

 

Transfer case finally let go but the good news picked up a 231j today can't wait to put it in