Interesting you say leaf springs, I keep thinking about these as I get a bit of bounce on uneven surfaces and on my SRT10 these are on top of the diff and pretty much flat with no load on them

 

If your bed is bouncing and jiving while you're driving, then I don't think it would be the LSD or the pinion bearing. Either of those would just send a vibe through the driveshaft. Maybe check your shackle bolts, and U-bolts.

Lucas

 

Checked the shackles and u bolts (u bolts were a little loose) but still have this problem.
It is FAR WORSE on a chip style road (not smooth) it vibrates way more and is noticable at different speeds on chip seal but on smooth it is slightly there at 35-40mph

I rechecked the shocks. Does anyone think it could be a problem with the leaf springs???

 

I FIXED MY DEATH WOBBLE TODAY! I it to the shop to have the castor adjusted as recommended my many of the forums. After the mechanic drove it he said it was not the castor. After checking it out he told me the PITMAN ARM and the IDLER ARM were so broken they were about to fall off the truck. They were both replaced. He did not touch the castor. I just picked it up and drove home. When I hit the bumps on the way home that always set it off nothing happened! As of right now there is NO WOBBLE!