Interesting you say that. The dealership called me this morning and said the truck was at their sister Ford dealership being diagnosed, but that it was NOT the transmission. He said he would keep me updated as he should have more info on what the problem was by Monday. We’ll see...Plugs. While it feels like a transmission issue, my guess is that it has original plugs with the gap open way wider than stock. Tuned trucks can go through plugs in 20k miles. I would read the codes and if it’s misfire codes, consider getting a steal on that truck, by replacing the plugs. Very common.