Well........damn I hate to have to add this but...on my way home (an hour ago) from Crestview Florida, I had an empty stretch of 4 lane roadway. Was doing 65 (posted speed limit) and literally nobody else around. So I decided to open her up and put the pedal down, not floored but down a good ways. It started at about 68mph and up to 90mph; the truck was shuddering. It's never done this before. I haven't done this enough to say its a habit. Anyway, as soon as I ease off the accelerator the shuddering goes away and it is smooth as silk, give it gas and it does it over and over. Feel it in the seat, not the steering wheel. It does not do this even on a hard WOT launch, it only starts at about 68mph and only under acceleration. Now I have added a Pedal Commander and the Range AFM disable since the last time I did this sort of driving, I will remove them tonight and see if this is somehow causing this new phenomenon. I can't guarantee a follow-up right away because it is RARE that I get a roadway that is empty and I do not endanger others. Some will point to the Pedal Commander and/or the Range but my suspicions are the transmission is starting to get the shudder others have had or still have. No CEL and no shaking at those speeds so it's not the tires.