Could be a bad Agitator Block - pull the tub out and make sure the block is locked in - also check that the locking nut is tight - these Vertical Modular Washers are notorious for work shock tower Rods - the New Ones are more rigid and stiff. Also there are small Springs around shock towers that are suppose to help. Also I've read that some techs even apply light grease to the shock tower cups to help.