It's not all that uncommon for a washing machine to make noise during the spin cycle. The drum spins at rapid speeds to wring laundry free of water and minimise time spent in the dryer. Sometimes the quick rotation can cause the washer to bounce up and down on the floor, especially when the wash load or the floor is uneven. There are ways, however, to lessen the noise and vibration that the washing machine produces without impacting its performance.
Make sure that the washing machine is level and all four corners are stable on the floor. The washing machine should not rock back and forth when pressure is applied. If it wobbles even the slightest bit, it's liable to pound against the floor and make a thumping noise during the spin cycle. Place a level on top of the machine and adjust the locknuts with a wrench at each foot until the machine sits completely flat on the floor.
When the wash load isn't evenly spread out in the washtub, it can cause the washing machine to pound against the floor when the drum spins. A balancing system inside the drum is designed to keep it equally weighted so that it turns uniformly when laundry and water are inside. However, the counterweights can only do so much to accommodate a lopsided wash load. At a certain point, the balancing system isn't able to adjust, and consequently the drum turns erratically, creating a banging noise. Stop the washing machine in mid-cycle and reposition the laundry inside.
Obstructed Water Pump
You can sometimes hear a pounding noise coming from your washing machine when the water pump becomes clogged. The water pump forces water out of the washtub as the drum spins the laundry. If a small piece of clothing or debris gets caught in the drain line and obstructs the water pump, the pump must strain to perform and may vibrate as a result. Until the clog is removed, the washer won't operate efficiently. Stop the washer in mid-cycle. Shut off power to the appliance and manually empty the machine of laundry and water. Review your washing machine manual for instructions on removing the drain hose to locate a possible blockage.
Most washing machines have a pulley in the rear of the machine. The pulley ensures that there's sufficient tension on the spin basket shaft so it's aligned when the washing machine operates. Inspect the pulley to make sure that it's firmly positioned against the spin basket shaft. Consult your washing machine manual for a diagram of your washing machine to locate the pulley. If the pulley is detached and loose, it can cause the washer to tremble as it spins. Either reattach the pulley or replace it if it's worn.