What kind of noises are you getting? Are they 'clanking' noises from the bobbin case, or whirring from the motor/gears, or something else?
Just curious on your 404: is the main motor drive gear a white plastic (like nylon) or is it a red/brown fiber gear?
I have a 404 here that has a white drive gear where all other 300,400,500,700 series machines I have seen have the red fiber gear.