You cant, the bearings and shaft and that motor or the blower wheel and its bearings are bad. AT this point live with it, because it's too old an furnace to put one peny into repairing. Any furnace thats more than ten to twelve years old, I do not repair because it does my customers a dis service to have them put money into something thats inefficient and will need replacement any way. If I were you I would just live with the noise--and not spend anything trying to remedy the situation other than replacement.