I don't remember if I posted this here or not but here's a picture of my pulley. As you can see the outer half started sliding towards my radiator. I replaced two serpentine belts before I found this and later found this is not uncommon. Just a heads up for you 8.1 guys to check this when you service your rig. Cause when mine came off I was about 5 miles from home on a winding road with no power brakes or power steering. Let me tell you it was all I could do to get it home.
Stan 2008 Bounder 38P, W24, 8.1L, 3 Slides 2019 tow dolly hydraulic brakes
Yep, that is the harmonic balancer which have been around for decades. They have been known to fail and can destroy a radiator when they do. The newer balancers are better than the old ones but this is still a press fit on to a flexible joint and they will eventually fail. Way back when you could tell the balance was starting to fail because your timing marks would start to shift.