"I think it was actually Al Gore that first coined the term Death Wobble.It was just before he invented the Internet."
Haaaa, there ya go there now, that 'splains it all!
Pretty sure Russ nailed the cause. No wobble on my '90 4WD Ram, until I swapped on some large, very worn unbalanced tires: instant wobble! I always considered a 'shimmy' to be that mild shake R/L in front end. The 'DW' effect on my Dodge is 10 times that, dramatic, a real wake up! Heard that with a manual steering truck it can rip the wheel right out of your hands, don't know personally.
Had to replace front axle u-joint on that truck, did help the wobble some, don't know why?? U-joints could be a lot beefier, especially considering it's a 1 ton.