I was driving on the interstate when it first happened to me. I entered a long radius 90 degree curve traveling to work at about 55 to 60 mph and about midway through the curve I drove over a bump and my truck began to shake violently and did not stop until I had decelerated to about 40 mph. My first inspection was on the front tires while they were suspended in the air, checking for any movement side to side or up and down in the wheel assembly. Everything seemed to be okay so, I inspected the u-joints next on the driveshaft. And, that is where the problem was. My very rear u-joint on the rear drive shaft was cracked and falling apart. Removed the 8 bolts holding the drive shaft in (4 front, 4 back), changed the u-joint out (pr. $15.00), re-installed the drive shaft and death wobble went away. I go through that same curve everyday I travel to work. I went through it at 60 mph after replacing the u-joint and hit the same bump, no more death wobble. I am thankful to have figured the problem out and fixed it before something worse happened.

 

That's a new take on death wobble. Usually it refers to steering. Good thing you caught that before it piled up and caused more damage!