The noise goes away.
We have run in both ahead and astern up to full revs. No noise with disconnected shaft
Of course, there was no load on the transmission like that.

we are going to try the Centaflex coupling, which has a good chance of working, but that is all.
Frustrating, since it will take a few day to get it, and we are trying to get ready to head up to Spitsbergen

I would appreciate you comments on the Centaflex. Particularly its design that uses ONLY a taper bush to grab the shaft. No key