What causes a washing machine agitator to hum?

The washing machine agitator is a component of top loading washing machines and creates a back-to-front or front-to-back revolving action that helps to wash clothes properly. Agitators can be either straight-vane or dual-action. Although an agitator is supposed to ‘agitate’ the machine, you may hear a humming sound from the machine. An agitator that hums is usually due to overloading the washing machine. A humming agitator may also be due to improper fitting of the agitator during a replacement. You can reduce the load of clothes to stop the humming. If that doesn't resolve the problem, check to see if the agitator is fixed securely.