And contrary to what I was hoping to accomplish, only the 390hp, 735 lb-ft version could be tested (the high output update from Ford had not yet been released). With the help from the folks at Randall’s Performance and their SuperFlow, we made a best pull of 349 hp and 667 lb-ft.
However, the new 6R140 TorqShift plays by different rules than we’re used to seeing. With no 1:1 gear available, we were forced to run the truck in Fourth and Fifth gear (Fourth is 1.15:1 and Fifth is 0.86:1) to see what the differences were.
In Fifth, and with 30 percent load, the truck laid down its highest numbers (349 hp and 667 lb-ft). However, its lowest numbers weren’t much lower: 340 hp and 635 lb-ft in Fourth gear and 25 percent load.
With the 3:55 axle ratio, our runs in Fourth gear spanned from 42 mph to 75 mph, and runs in Fifth gear ranged from 52 mph to 95 mph. Running the truck in Sixth would be out of the question, as it’s governed from the factory at 97 mph. Check out the dyno graphs below. Our torque curve explains why these trucks pull like freight trains. Peak horsepower is achieved at 2,800 rpm and the torque flat lines from roughly 1,850 rpm to 2,850 rpm. Cummins-like?