When my furnace shuts down, it makes a loud "grinding" or vibrating noise.
Tech adjusted the motor speed and all alignnents, but can't figure out problem.
Model # G61MP-606-091-09
Serial# 5911G-15239.
LENNOX ELITE

That's going to be a tough one to figure out without being there to hear the noise for myself. Lots of options here, just to many to even guess. Is the tech sure the noise is coming from the blower assembly, or could it be coming from the draft inducer, or ductwork etc?