Part that Should be on Mower Deck

[lawncutter]

This is the part that supposd to be on my machine so the mandrel spindle does not keep breaking I think Sears needs to replace my money for the parts I bought.
The machine is 2011 YT 4000 Craftsman on the 42 inch mower deck. The stripper plates are the red one part #174493
Sears say that my machine does not supposed to have one. The new mowers a sunk in the mower deck to prevent this. Nickel Dime