Have HVAC Questions? Ask an HVAC Expert for Answers
What squirrel cage? on your furnace blower?
It's possible that the set screw that secures the squirrel cage to the motor shaft has come loose. When that happens the cage can slip out of position and grind on adjacent surfaces. You need to remove the blower and re position the cage so it doesn't rub against anything and spins freely. It's also possible the bearings are gone (much less likely) and you need a new blower.