Noisy Fluval 404

[rvm]

I have a Fluval 404 that I aquired with my new tank, and it is a noisy bugger. I have 2 204's and they are practically silent (one is in my bedroom and I can barely hear it at night!!!) so I figure there is something wrong with the 404. I tried replacing the ceramic impellor shaft, and it made a bit of difference, but it still vibrates and rattles constantly. Does anyone know what could be causing this??

 

[elgecko]

What about the clear cover that snaps over the other end of the ceramic impellor shaft?
Seated right? Elongated hole?
Just throwing out some thoughts.