I have had problems with front end shake on my 2011 3500 HD Dually and a seeming loss of braking power when towing our toy hauler. The dealer service manager told me that he has a dually and "replaces brake rotors and pads all the time." That was last year so I opted to replace all for rotors and pads with Powerstop drilled/slotted units and ceramic/Kevlar pads. All was great after that for the few times we towed the fifth wheel, then this past week we took a trip for Washington to Montana, crossing a few mountain passes. That's when it started all over again, with the pulsation/shaking increasing as brakes were applied at intervals heading downhill. It's darn scary when one has a 40'15,600lb load behind and these brake issues crop up.
I also don't get a sense that the engine brake is all that effective on this truck under at-speed applications. I can greatly sense the engine brake effect when the truck's empty and moving at about 40mph downhill but not with a load. Engine RPM has to increase to a seemingly freewheeling state before the engine brake kicks in... I don't get it.
Going back to the dealer today for more analysis. I captured a video of the steering wheel shudder to show them. I hope they actually do something to FIX the brake issue. It would be great if it's the brake pedal assembly, but I am not holding my breath. I just hope my fancy-dancy slotted/drilled rotors aren't now trashed.