Why is my washer vibrating, rocking, or 'walking' during a cycle?

This is most commonly caused by the front and rear feet not being in firm contact with the floor, or the washer not being level — jam nuts must be tight against the bottom of the cabinet. It can also be caused by an unbalanced or tightly packed load, shipping bolts still being in the back of the washer, or uneven flooring. A 3/4" (19 mm) piece of plywood placed under the washer can help reduce sound if the flooring is uneven.