2012 Peterbilt 386 - Steering Wheel Jerking Back and Forth Violently

might try customer service, recall?

 

The pitman arm is loose on the sector shaft... I'd bet on it. It doesn't take much looseness at all for it to cause a harmonic death wobble. Turn the input shaft by hand while you look very closely where the pitman arm attaches to the shaft. If you see the shaft move even the tiniest bit before the pitman arm moves, there's your problem.

 

Check everything these fellows have mentioned and if it all checks out, have your tires broke down and have them check them for a broke belt. Happened to me and I was skeptical when the tire guy told me what it was but when he broke it down I sure put a little extra in the offering plate on Sunday.