I have a 2018 RAM Dually and recently installed the Torklift 20k Superhitch and it does use the factory hitch as the top tube. It piggybacks both the Torklift and RAM hitch and they are bolted together to form a single twin-tube unit. I believe that I used the D1108 because the frame on the 2018 is different than the 2017 and earlier trucks. The Torklift also bolts on to the RAM’s side plates underneath. As usual the Torklift instructions are not very clear but you can figure it out as I installed it myself.
TG
