The inside tub moves on the spin stage only and cause the water, by a centrifugal force, to be forced out of the clothes. During the wash cycle,the tub is stationary and the agitator moves forth and back. If you would like to remove the agitator - Remove the inner agitator cap (inside the top of the agitator) and then open the screw (be aware not to lose parts !) Good luck !
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