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The rotors on the Super Duty trucks can be a real pain to remove. I would spay the hub of the rotor and all the studs of the rotor with some sort of penitrating oil. Let this oil sit for a few minutes. Then the next step will require a second person as they will need to have a pry bar and try prying the rotor from the backside holding pressure on it. Then take a sledge hammer and hit between the studs if your saving the rotor or just hit the rotor and it should come off. Also, you pretty much have to hit the rotor as hard as you can to get it off. As you can see there really is no trick just a little bit of brute strength should make the rotor pop off the hub.