I just got a complete brake job done on my Doge Ram,Van 3500, I had to bring the van back because the brakes were chattering. They resurfaced the new drums which were out of round. That didtn't fix the problem so they ordered a new set up drums which turned out to be out of round also. After resurfacing the drums again the problem was not as noticable but is starting to feel like driving on a washboard again when I apply the brakes. Anyone out there have a clue about what could be happinning other than warped rear drums? And a bonus my abs light and brake warning light just came on, I replace the speed sensor on the diferential but that didn't help....

 

Ateach of the wheels there is a ring with with teeth that looks like a gear. This is what rotates with the wheel as the teeth pass by the ABS wheel sensor. It's likely that one of those rings cracked/split or a tooth broke off. You'll have to slowly rotate each wheel as you watch the teeth for any signs of damage. If they all check out, then one of the wheel sensors could be bad. Although, I'd opt for the bad sensor since your ABS light did come on.