I don't even know for sure what it's called. On my Trek 7200 I've noticed that the freewheel clicking sound (the one you hear when coasting or turning the pedals backwards) is non-existent. I don't know if it disappeared or if it wasn't even there in the first place (though I am pretty sure it was), but it isn't there now. The wheel feels fine, the gears shift perfectly. Is this something to worry about?