whirlpool washer makes a loud knocking noise M#GHW9150PWO?

Front load washer makes loud knocking noise during spin cycle. I removed the bottom access panel below the front door and all stablizing shocks appear to be fine. Inside the front door where the tub meets the door underneath the grey rubber gasket a white plastic piece has a groove worn into it. I reached into the tub and it feels like two of the three grey fins are loose. Is there anything I can do to repair?

Bob
January 2011