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If your washer starts shaking during the spin cycle, pause the washing machine. Open the door to inspect the arrangement of your clothes. If there is an uneven pile, your drum may have simply bundled your clothes into an uneven ball. Spread your clothes out and resume your spin cycle. If your washer continues to shake, remove some of your clothes. You may have simply overloaded it. If your washer consistently causes your clothes to bundle together into an uneven ball, the drum is probably absorbing weight unevenly because it isn't level. You may be filling the drum with too many clothes when you use your washer, even if it doesn't seem like it. Only add clothes until the drum is half-full so that the clothes have room to move when the drum spins. For a front-loading machine, pile your clothes up higher towards the back of the drum and avoid leaving them near the door. Overfilling your machine will also keep your clothes from getting adequately clean. To see if your washer isn't level, put both hands on the top of your washer. Try pushing it side-to-side. If it wobbles or gives at all, your machine isn't level and the vibration from the drum is making the legs bang repeatedly into the floor. Find a more even section of flooring and move the washer to see if the problem stops. If your dryer is unlevel too, then it's probably your floor's fault. Try finding a flatter area of your home to set the machines or slide a sheet of plywood underneath them. Open a front-loading washer and try to press the bottom of the drum down. If it doesn't move at all, the delivery or installation crew probably forgot to remove the shipping bolts. Turn your washer on to its side. Look underneath the machine and behind it for plastic clamps that are shoved over the openings or bolts. The shipping bolts ensure that your drum doesn't move during delivery and installation. They will cause a machine to shake if they're left in. Depending on the make and model of your machine, the shipping bolts may be hiding behind the back panel. If your back panel simply slides out, lift it up to see if there are any plastic pieces latched to your drum. Remove the shipping bolts by squeezing the handle and pulling them. If the bolts are screwed into a panel, place a wrench over the bolt and turn it counterclockwise to loosen and remove them. Sometimes, you can simply unscrew the bolts by hand. The shipping bolts are usually brightly-colored so that they're easy to notice. They also tend to be made from a cheap plastic. They should look really out of place on your machine.
Move your clothes around in the middle of a spin cycle. Use smaller loads of clothes when filling your washing machine. Try rocking the machine when it isn't running to see if it tilts and move it. Look for shipping bolts on the back and bottom of a new washer. Remove the shipping bolts by hand or with a wrench.