Ford super duty 3.31 rear end. Will it be a big mistake. ?

I think the Cummins holds higher back pressure so it might provide adequate braking without the need to rev the engine beyond 2000 to 3000 rpm. The Powerstroke red lines at 4000 rpm and to provide the level of braking the Cummins does it needs to be revved higher. The exhaust brake on the 2015+ Powerstroke works extremely well with lighter trailers such as our 16000 lb rvs. You simply set it to auto and start descending the grade, the back pressure varies to keep your speed constant. If you want to increase your speed slightly you can touch the throttle and the new set point is whatever your speed is at the moment you let off the throttle. If you want to slow down you can step on the brake and the new set point is whatever the travel speed is when you let off the brake. Automatic wheel braking isn't used until engine redline is reached, which is very seldom with a 16k trailer. I haven't driven the 10 speed yet but having more gear choices will allow us to dial in our speed on the downgrades even better.