I've been using this X case for 6 years. It's always made a gear radling noise,when driving. Is this common? Our do I need to rebuild?

Gears don't generally make a rattling noise. They tend to whine when things aren't right. Shift forks (hi/lo or 2wd/4wd) are much more likely to rattle when they are worn excessively.
Does it make the noise when you change rapidly from acceleration to deceleration and back? If so, maybe excess thrust clearance on the idler or output gear.
Does it make the noise when you rev it up and down with the T case in neutral with the tranny in gear and the vehicle stopped? If so, it is not the shift forks.

If it is just rattling and has no other symptoms of impending doom, like a shining noise that changes when you accelerate and decelerate or chunks of metal on the magnetic drain plug, I would just run it until something until you have a more significant problem.

It rattles alot more during deceleration. Just a little during acceleration. It does'nt make any noise in neutral. I just wondering if this is common in the LC X case.

Originally posted by Arnett
It rattles alot more during deceleration. Just a little during acceleration. It does'nt make any noise in neutral. I just wondering if this is common in the LC X case.

The major wear points and failure modes of the Toyota J30 case are the idler gear center shaft/bearings, the lo gear bushing and the shift forks. Since it doesn't make noise with the transfer case in neutral and the transmission in gear, chances are that it is not the gear and bearings, but rather the shift forks.

Change the gear lube and check the drain plug. If there are a lot of metal flakes as opposed to fine dust on the magnet, you might want to rebuild it. Parts are about $150. If the forks are worn, you can just build them up by TIG welding a bead on the worn area and filing it to the slot width.