Sounds like you will need a new transmission. Pull your agitator and check it first for any hang up in your agitator dogs or something else. If that is ok, likely problem is the tranny.

It is a little expensive, but given where you are on the tear down it is not much more work. Just take off the agitator, then remove the three bolts holding the transmission and pull it out. Slide the new one in and off you go.

Good luck, hope that fixes it for you.

machine will spin but will not agitate pulled motor and transmission off of barrel and turned shaft will spin one way fine and will srin other way then lockup