Product review (5 stars): Easy installation. Fixed my machine.
If your washer doesnt spin or agitate, the first thing you should do (if you know the motor works) is tip it up a little, and with the cycle running, look to make sure this part is spinning (between motor and transmission), and spinning evenly.  If yours is spinning and you end up making other repairs I would consider replacing this anyhow while you're in there. They all fail eventually.