the dry side was very chattery and we determined that it was two bearings that had probably worn out (in hindsight it was only one and it was already off the main "impeller". So I took the dry side apart according to
this thread. Technically it is the dry side impeller that drives the wet side impeller. Both have magnets on them but the dry side one isn't replaceable as it is proprietary and you have to buy a whole new dry side to get it.