The growling may be motor growl which can be remedied with some drops of oil on the bearings as mentioned earlier. I had a machine one time that growled so bad I pulled the motor and put in a different motor and it still growled with a different motor in it. I re-oiled everything I could think of and it still had a pesky growl and it sounded like the motor was dragging and not turning right. I spent a lot of time on it. Finally laid it on its side and shot some oil into the bobbin area from all directions and ran the bejeebers out of it and all of a sudden it sounded a whole lot better. I think I had cleaned and oiled that machine months before that... Not for sure.... My theory is that some times even new oil can dry and clog up and cause growls. I prefer to re-oil a machine that has been sitting.