After changing some of my torque rod bushings and seeing how bad the 20 year old rubber was I started thinking about the
engine harmonic balancer.Searched the forum and mostly found info on the dampner on the trans side.Did some research and
found some things to look for,excessive vibration,rubber missing,the rubber ring protruding unevenly.Found alot on the diesel
forums on the 5.9 balancers but not much on the 12 valve 8.3.I don't think mine is bad but I'm not sure how a new 8.3 would
feel and vibrate.
Just throwing the post out there to get some thoughts and ideas going.The part number on mine is 3925560 made in Mexico.
There are some places that will rebuild yours also.Found new ones but most made in China.
Just found the posts on "vibration dampers",looks like after 2 more years there is still no fluid replacement for the 8.3.
Sounds like you found the thread from the last discussion I remember on this subject. Link below in case you missed it. I never did anything about replacing mine, and it still looks exactly the same 2 years later. If you come up with any new information pertaining to stock or aftermarket replacement units, post it here. This is one of those engine components that gets very little (if any) attention from 98% of coach owners. With the high total miles on some of the coaches, and only one reported failure that I am aware of, the damper is apparently a pretty reliable chunk of iron and rubber.
Cummins Vibration Damper (http://www.foreforums.com/index.php?topic=21962.msg165127#msg165127)