I have had this issue on my 2016 NV 3500 HD Quigley. And it does not just happen on steep grades but if you hit the breaks hard at high speed say 50 mph +. You do not feel the break pedal pump like normal ABS engagement. Instead the steering wheel shimmy's from side to side. I have replaced my front rotors three times in the last two year. My Mechanic says they are warped, and he has to replace them each time. They are under a three year warantee. But come on. The last time we replaced them was in May, and I started to feel the shimmy again this morning. There has got to be a permanent solution.