Originally Posted by
dsaul
It sounds like the chain is routed on the wrong side of the metal tab on the derailleur cage. The chain should not touch the tab that sticks out from the derailleur cage, between the jockey wheels. It is a pretty common error and the chain rattles as each link slides over that tab.
It does sound like that, but it doesn't make this noise at all in the smallest and middle chainrings - wouldn't that rule it out? I can double check the chain routing, but it looked right to me.