Outer Limits 4x4 Board

Hey guys

The odd sound appearing every once in a while in my disco is not from my CV as I dismantled and everything is ok.
It seems to be coming from the transfer case according to my mechanic which I trust ?
Is it possible ? What could it be a damaged gear bearing....?

Thanks
Jay

Sample the oil if there is metal in it thats a good indication things are nasty, maybe excessive backlash in the centre diff or worn layshaft, stuffed universal, plenty of possibilities.