F350 transfer case

I posted a question yesterday concerning a noise from the transfer case. I mentioned it sounded as though the transfer case was coming through the floorboard, well, it is, or at least trying to.
Under load, the yoke is raising up and rubbing on the floor pan. We have checked every mount and bolt and found nothing cracked, broken or loose. As I mentioned the truck has a 6" lift. Any Ideas?
Thanks.