I have a 1999 Xj 4.0 the with 242 the other night while driving home in 2wd i heard a strange drive train knock so i pulled over shifted it to 4 then back to 2 thinking it might not have been all the way outta 4 to begin with... about 2 miles later i slid off the road into a snow drift i put it in 4 to back out.. no 4wd anymore.. i got outta the drift in 2 but while driving home i heard a Whining noise from the front end????

Whats going on?!?!? any ideas would be awesome!

 

Impossible to say for sure from your description, but if the shift linkage isn't out of adjustment T/C could be SOL.