I have a 2001 GMC 1500 4wd pickup. I just replaced front rotors and brake pads, hoping it would solve this problem of grinding, but it didn't. We are not sure what is causing this. It only grinds when slowing down and speeding up, up until i get over 20 mph. When I am doing a steady speed and have to stop at the light, immediately when I stop, the truck does a quick "shaking" after I brake. Does anyone know what I'm talking about? My boyfriend thought it might be driveshaft not having enough oil or lube in it and my dad thinks it might be a wheelbearing?