i have a 1970 3/4 ton c/s every know and then ill hit a bump in the road and the front end will start jumping and violently shake the truck untill i get it under 20 mph any thoughts

 

alignment, radius arm bushings shot, kingpins shot, shocks shot, bearings packed or need new?

 

I'd actually do a visual inspection of the suspension and steering components and look for broken, loose, or worn parts... even a cracked frame. Then I'd wiggle, crimp, jostle the parts. Maybe even jack up the front end to cycle the suspension and steering. I'd probably even verify the the motor mounts are still in one piece.

I must be crazy.

 

2 or 4wd? Solid axle and you could have a death wobble going on.

Like this. (Skip ahead to 1:00)

 

If I had that going on in my truck, I think I'd have BOTH hands on the wheel!