Product review (5 stars): ... agitator stops spinning but the motor is working just fine, you probably just need to replace these
If your agitator stops spinning but the motor is working just fine, you probably just need to replace these. Figuring this out was a huge relief to me! They were very easy to replace in my washing machine and saved me a lot of time and money over buying a new one or making a service call. These seem to be good quality and now my washer is working as well as it ever has. Amazon couldn't find my (ancient!) washing machine model to check for compatibility but it is a whirlpool and these were an exact match. The only tools I needed were a socket wrench, a extension bar (at least 8 inches), and either an 11mm or 7/16 in. socket.

If you have a washing machine with an agitator, you will have to replaces these at some point as they wear down with use. The original set in my washer lasted 8 years, but I'm not taking the chance of having these go out at the most inopportune time again (3 days before I was expecting a house full of out of state guests for the week when I hadn't done laundry in almost two weeks!) For the price of these, I'll keep an extra s set on hand just in case.