My washing machine - WSM2700HAWWW (part of washer/dryer stackable unit) will not agitate during the wash cycle. It fills with water and it drains/spins water fine, but it doesn't clean the clothes because the clothes are not moving anywhere. The agitator just barely moves. I have read somewhere about replacing the coupler, but my model does not have a coupler, it has a belt. Should I replace the belt or another part? Thanks for you help!

Thanks for your reply. We fixed the problem - which was a broken drive block. $24 part seems to be putting our machine back in great running condition. We figured this out by noticing that the agitator cap was spinning as expected during the agitator cycle; however, the agitator itself was totally loose (I could spin it around in my hand easily). I noticed in my research that people said to look at replacing the coupler, but I was told my machine does not have a coupler... well it does... at least it serves the same function but goes by a different name - drive block. Now, to start catching up on laundry.