Originally Posted by
bikernew
Is it NORMAL to have a good deal of chain "chatter(clatter)" in the lowest(yes, largest) 3 or even 4 gears of a 10 speed cassette when riding on the large chain ring? I've got my limits and indexing set perfectly, after several attempts and including a complete RD cable cleaning and lube.
Another possibility is that your rear derailleur hanger is slightly bent. A bent hanger could result in the derailleur being properly aligned with the smaller cogs but out of alignment with the larger cogs on the cassette.
Your shop can check the hanger alignment for you if you don't have access to the
tool yourself.