Gas Furnace Vibration

[Jim C]

Try this, during the summer when your heating system isn't being used, remove the motor with the fan attached (if you can and as you mentioned no belt). Find a competent electrical or machine shop and have them look at it..or do you know anyone who works at a power plant?
Jim C

[ready or knots]

I have had this problem before with ,janitrol and goodman gas furnaces ,1 the burner had crack in it causing cross fire,this sounded like loud bumping and thumping .second one was cracks in heat exchanger,this
sounded like, buzz and banging noise also made noise when cooling down after cycle . both units had to much gas pressure. good luck hope this helps.