I've got a 2008 Chevy 4.8 engine. Trying to figure out this noise. A little background. The noise sounded like maybe a broken flywheel so we pulled the torque converter cover down and looked the best we could for cracks. We did not see any visible ones. So we ran the engine with the cover off to listen for the noise again. The flywheel and torque converter were wobbling so bad it made us jump back a second. We figured we were onto something so we pulled the trani and found the torque converter hub and hub bushing shot. We wondered this could be the noise. We had the bushing replaced and a new torque converter installed. We also replaced the flywheel just because of how bad the wobble was we figured it stressed the flywheel pretty good. Upon starting the engine the noise seemed to be gone. Then after about 5 minutes of running it came back. Now this noise started off as very intermittent. Some days it would not do it. Then it would do it for a week then go away again. Now it is pretty much always there. Engine cold or warm does not seem to matter much it doesn't go away. Hear is a link to a video we took the other day. Now the wobble you see in the flywheel was about four times worse before we did the torque converter and bushing.

https://youtu.be/ypm5OmlDI7s

My theory is the wobble whiped out the crankshaft thrust bearing. I did did not mic it up yet but I quickly took a pry bar and could easily move the crank back and forth 20 thousands of more which is way out of spec. The noise at first may think lifter but listen closely and it seems to have a rotational rub or scrape noise to it.

Please any help would be greatly appreciated.