It looks like that complete center section is toast- - - - -Try removing the two bearing saddles to see if you can create some slack somewhere. They're held on by the two big bolts on each side of the ring gear. Just keep up with the position to the saddle clamps on the remote possibility the center section can be reused. Identify them with some center punch marks, side to side and top/bottom so they can be reinstalled in the proper orientation.

If the ring gear isn't turning, the clunk noises are probably coming from a broken U joint.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!