My 30+ year-old top-loading washer has recently started having a problem with agitating. It fills fine, but when it finishes filling, when it's supposed to agitate, it just sits there humming. The motor hum is louder when the agitator isn't agitating than when it is. When the washer first started doing this, it did it occasionally, and would start to agitate on its own without intervention after a few seconds. Now it will just sit there and hum and not agitate unless I intervene. I can usually get it to go if I turn the agitator by hand, or sometimes by spinning the tub. A few days ago, it seemed that the agitator wasn't all the way down in the tub, so I used a hammer (on a folded cloth) to bang it back down. The agitation problem went away for a few days. However, it is back to needing me to get it going by hand. The washer has 3 cycles, and 2 of them stopped working years ago. But all the facets of the normal wash cycle worked fine until the agitator problem started. Once I get the agitator to start agitating, it works fine throughout the cycle and doesn't need my help with the rinse cycle. Could someone point me to the possible source of this problem? Thank you for any assistance.

It was suggested that the problem might be the spline in the agitator having worn out. However when I took the cap off the agitator and watched it, it was both the shaft and the spline that did not turn...not just the spline.

Is the motor going bad, or is there some replaceable part at the base of the shaft?

Thanks.