Clunking/rattling sound on hard acceleration

I have a 99 XJ with 4WD(command trac) and 4.0L engine, auto trans.
When I accelerate hard from a stop, I get this clunking/rattling sound as I accelerate. It goes away after a second of acceleration. I thought maybe it had to do something with the front driveshaft or u-joints(just guesses).

I recently tried to do this same thing but with 4WD HI engaged. When I accelerated, the clunk/rattle upon acceleration was gone.

Any ideas as to what could be causing this?
Is it normal or not?

Thanks,
Manuel

Is your rig lifted?
If so, how much?

If you are stock, you probably suffer from axle wrap. I also suffer from this, stock leaves just plain worn out..