Agitator would not move during wash cycle

I placed both hands under the agitator 180 degrees apart, gave a quick jerk, and seperated the agitator from the coupling. With the agitator removed, use a socket and ratchet to remove the bolt holding the coupling to the spline. Remove the old coupling and slide the new one over the spline. Lightly tap on the coupling if necessary. Insert the bolt with the ratchet and slide the agitator back over the coupling and you are done.