chevy

Hi I’m a first time diesel owner and a first time dually owner. I’ve owned trucks my whole life but I never owned a truck like this or a Diesel engine vehicle. I bought a 2009 Chevy silverado 3500HD duramx turbo diesel 6.6 with 35k recently and I'm just looking for advice on anything important...

I am not getting full "power" out of my intagraded brake controller. The trailer brakes are barely working on any trailer when the controller is turned all the way up. Could anyone point me in a direction to figure out what is going on?