This may be of no help. I had a similar problem with a Jeep Wrangler many years ago....I had it aligned, checked re-checked still would get death wobble. By luck I found the problem. My rear track bar was loose, causing the rear axle to shift just enough to throw the alignment out and cause the wobble. Now I know that a Jeep is very different 1 ton duelly but maybe my experience has some relevance? Probably not