I have been running into this for too long now. I test a top load whirlpool style washer and often get the loud knocking noise from the transmission during agitate. As the transmission is too expensive too replace and resell the machine for a reasonable profit I end up scrapping it out.
I do have the time to putter around and rebuild the tranny myself BUT what part is it that actually causes the knocking. They are a pretty simple unit and many of the parts are available but again too expensive too try just replacing parts as a test or learning experience. I don't believe it's a combination of many parts worn out. I think it's one part that really causes the problem I just don't know which one and I'm sure someone has figured it out ahead of me.
So I ask if anyone has gotten into the innards of these transmissions and knows for sure which part it is that is causing this way too common problem. I'm tired of scrapping these things out.