does sound like a synchro is going..... has the tranny fluid been changed/flushed recently? what does the tranny fluid look like? if if hasn't' been done since you've owned it, do it. might have water in it or something like that anythings possible
jeeps make noises. just remember, when they STOP, then you have to start worrying........................... means whatever was makin the noise has kicked the bucket.
something to keep in mind, if ur gonna wheel, learn to change fluids; cause its easier to change them 3x a year than blow a tranny/tcase/diff................