It ends up the reason for the noise in our furnace had to do with how the furnace was assembled by Suburban. Apparently the "squirrel cage" location is somewhat variable (probably with bolts that have adjustable holes to go through so you can fine tune the location?).
In any case, the tech at our dealership had heard the same sound, albeit much sooner, on a couple of new trailers with Suburban furnaces. He recognized it right away. (Yes, I was able to reproduce it at the dealership!
) To fix the problem he had to remove the furnace - not an easy task on the 23IKSS as there is no access from the outside and where they put it would be tough for even a squirrel to access!
Once he had access to the furnace he readjusted the position of the squirrel cage so that it would not hit whatever it was hitting. Problem solved.