Yes, upper King pin bushings and springs. The reason for springs is to give some play while still maintaining even lower bearing preload with a cylindrical bushing...ok, it is conical but same ideal. Now if it were a ball joint, there would be no need for springs and bushings but who knows the engineering decision at Dana.
Death wobble is nothing more than precessional oscillation, much like a toy top wobbling. The speed at which it happens is based on the mass of the rotational assembly (wheel) and the spring force of the bushing springs. Actually the spring constant, works out to frequency or speed is an equation of the square root of the spring constant divided by the mass...but that is highly simplified. Any how, when the springs get weak or the mass increases, the frequency gets into the range where it is a problem.