Uneven floors or washing machine feet that need adjusting can result in a washer that won’t sit level. A washing machine that sits unevenly can result in excessive vibration.
If you think your floors are a problem, try using a piece of plywood to serve as an even surface. Then, adjust the machine’s feet, using the lowest adjustable setting possible that will still allow you to achieve stability.
The closer your machine is to the ground, the better. Some units have self-adjusting rear legs. To adjust these, carefully tilt your washer forward until the legs are about 3-4 inches above the ground. Then, slowly lower your machine again, and the legs should adjust, so your washing machine sits flat.