Spin cycle has become out of balance

The vibration damper(s) may be broken, disconnected, or worn out. Remove the top so that you can see the sides of the outer tub (assuming a top-loader machine), and shake the outer tub in various directions while watching the damper positions. There should be at least three such dampers, maybe more, and they can be several types from friction pads to tiny automotive-looking shock absorbers. If the tub seems offset to one side, look for one of the absorbers that may be out of place or disconnected. Hope this helps.