I figured I had to replace the drum support rollers, as if they're worn out and wobbling on the shaft, that could be part of the noise issue. After disassembling the unit, I also discovered the blower metal insert molded into the blower wheel was loose (it was no longer securely molded into place). Because the metal insert was loose, there was not an easy way to remove the blower wheel from the motor shaft because the molded in hexagonal nut was 'disconnected' from the metal insert. A quick internet search showed me how to use a hole saw to remove the wheel and then grip the metal insert with locking pliers. That internet trick was a lifesaver.
Reassembled and it now runs nice and quiet.