Hello from NH:
I have a York GY9S*UP furnace (4 years old now). Recently, I noticed that the blower noise (no heat, no a/c, just fan circulating) is much more loud than what it used to be. There is a loud sucking sound when the fan starts and then the noise settles down to what I can only describe as high speed air movement being obstructed by metal plate or foil. The noise is more audible at floor registers nearer the furnace.
I vacuumed the furnace blower squirrel cage with shop vac. Filter is clean. Removing filter, increases the noise level.
I am suspecting motor bearings.