Transfer Case Issue (?)

[CLS70]

Hi -

Seems I have a Transfer Case issue - was checking the front suspension and found that, with both front wheels in the air, if I move the wheels rapidly back and forth (e.g. 20 degrees back & then forward) there is a very loud metallic clunk coming from -I assume is- the transfer case almost like it had no "grease" or if there was a huge play (loosen) connection somewhere.....

Any suggestion? I guess I need to start shopping around for a new one (not sure if just changing the fluid will resolve this.....) the CV joints seem ok (boots are fine and there are no signs of deterioration there)......plus the sound comes from within the center of the car vs the joints......

Thx