Have anyone had problems with the transfer case? Can this part be rebuilt?

May not be the transfer case. There is a TSB for the GX for driveline clunk. Replaces the propshaft. Also check the front diff support arms. I've seen on GX with a broken one.

I agree with the other post, Lexus rarely recalls so I would always ask a Toyota dealer (cheaper labor rate) than Lexus if they can look up tech reports TSB's to see if there is any info.