Carrier Weathermaker 8000, probably from 1998.

CR-318984-753 was replaced and now we have this loud vibrating sound whenever the furnace kicks on and runs and it wakes up the whole house. Repair will be out here tomorrow for the third time. They tell me its not fixable. I don't believe it.

Any thing can be fixed. That part number is the combustion blower motor. Have them pull the whole housing off and check the blower inside.