I have a Shimano Ultegra RD, number 6603 for 10sp with triple front chainring.
I know that the two cogs in the RD cage are supposed to be perfectly vertical with one another when viewed from the rear of the bike, but mine seems to not be. When viewed from above, it apears that the top cog is lined up with the left chain plate of the chain. This means that the difference between the top and bottom cog is half of a chain width. IOW, the cage seems to be bent slightly outward, AWAY from the spokes. I know the common damage to RDs comes from crashing on the drive side of the bike and bending the hanger or the cage TOWARDS the spokes, but this one is bent the other way. Not only that, but there apppears to be a slight twist to it as well, like the bottom cog is twisted a little with teeth nearest the front of the bike pointed inward. Does this make sense?
I've never disassmbled an RD before, how difficult is it? If I take the cage plates off the RD, will it be easier to see if they are twisted? They don't appear to be while the RD is on the bike. Also, the bike shifts fine and is not making any noises during operation. Could it be the RD hanger that is bent?