How do I fix my Kenmore 110?

My machine Model 110 82873120 serial c94339499 is a dual action agitator. I do not think it is agitating right. The bottom part does but the part that sticks out of the water does not . I can easily turn it round and round but if I apply pressure to the top of it , it will turn the water. again the bottom part of the agitator does work but the neck part does not . Is it loose or what please let me know how to fix this.