Death Wobble, is what you feel when driving the truck. It feel slike someone is standing on the running boards, or side of your truck shaking it as hard as they can while you are driving. the only way to get it to stop once it starts is to slow down, almost to a complete stop sometimes. I know when my truck had it real bad, mine was from a bad tire, if it started the "death Wobble" I would slow down, and I know other people in other vehicles could see the truck shake too.
It also seems to happen, or at least for mine, when ever I hit a bump with one tire, or hit a bumper first with one tire then the other, but it wouldn't do it unless I was going over 40MPH. Even with my bad tire, it had a big chunk out of the side where I ran over a nissan 300zx, if I had enough PSI in it, it would stop altogether.