Does it seem to do it more after the breaks get warm/hot? Does it do it fist thing, or after you've used them a bit? My 300 would be OK, till you used the breaks (getting them warm-hot), and had them warmed up. Then it would do about the same thing (getting progressively worse as the heat built up). This was due to "hot spots" in the rotors. I replaced the rotors, and problem gone. I know, you replaced them a while back. But that doesn't mean the rotors are still the best (don't know where you got them, how good a product they are). How long after you replaced the rotors did the problem expose it's ugly head? Did the breaks do this with the first set of rotors you had on the truck?