Older Gator 4X6 clutch/shift problem

I have an older 6X4 Gator - well used.
We replaced the drive belt - did some electrical work, and in general started the obvious restoration tasks. The few test drives appeared fine, but now, the clutches apparently are not fully dis-engaging - to allow proper disconnecting - and shifting.

I have not had the opportunity to actually begin to troubleshoot yet - looking for any suggestions where to start -

Symptoms are internal transmission shaft never stops - to allow proper shifting into either forward or reverse - gear grinding when attempting to put into gear.

Suggestions please
Thanks
Jeff