205 transfer case guru's needed....

I would be leaned toward the solid mount causing the noise. I’m running a 203/205 married setup in my truck with no transfer case noise. I do have rubber mounts. I’m praying for you that’s it’s not the case itself. That sumbitch is heavy.
Even as old and archaic as the M37s are, they still used rubber biscuit mounts to mount the transfer case. lol