The Rear Anti-Lock light came on. I recently replaced the power steering pump (another thread). Additional symptoms: 1) There's a vibration when I brake that doesn't go away until the truck stops, even if I take my foot off the brake;I feel it all through the truck like its coming from the rear; there's a pulsing to it, like driving across a metal grate bridge; 2) sometimes, when I first drive in the day, I feel the back end cycling up and down, almost bouncing; this goes away after a few miles. Any ideas/suggestions appreciated.