So recently I went to fire up my 2001 2500hd chevy silverado, it has a 6.0L Vortec in it and has been very reliable, 129,000 mile. But when I went to start it this morning, I turned the key and the entire truck shut off, like the battery had died, so I got out of the truck and checked the connections to the battery and tightened them a little and went to start it again, this time I turned the key over and the truck stayed on but the starter was not clicking, to reiterate, first time the entire truck shut off and had no power, second time the dashboard and other electric components stayed on but there was no clicking from the starter. So my initial thought was that I had a bad starter, as such I towed it around back and went and got a rock to try and clip the starter to get it to start one last time, to make sure the starter was the issue of course, I got under the car and had my brother get in the driver seat ready to start it when I hit the starter, as I got in position I had him go ahead and turn over the ignition and to my surprise, the truck started, without having to hit the starter. But when it started it had this noise https://drive.google.com/file/d/0B-D96-MrhsgUdG5tSGF6UlFBNG8/view . It did idle though but the noise did sound internal, we shut it off and tried to research what it could be to no avail so we decided to start it again to narrow it down to where the noise was coming from, we started it and it idled for about 5-7 seconds then the truck stalled, we searched the symptoms and only found bent rod, but we went ahead and called our mechanic uncle who's worked as a mechanic his entire life and he said he thinks it's the flywheel but he lives far away so he only got the same video linked above, so I thought I should consult a few mechanic forums before I either started searching for a new engine or tearing into replacing the flywheel. Thanks for reading and I can't wait to hear back from everyone!