Hey guys. Iv got a 2011 gmc seirra 2500HD. regular cab long box 6.0L automatic. We been having a issue where when pulling our dump trailer loaded with material driving down the road and when stopping the steering shakes violently. We checked the complete front suspension ball joints were all good we replaced the idler, pitman arm, center link, steering column to gear box shaft plus added a steering stabilizer as well. tires are all wearing nice and straight to. We also done brake pads and rotors. This truck has been pulling trailers most of its life. Any help would be greatly appreciated. I have done everything I can think would be the issue. thank you in advance