I have a 2002 Jeep Grand Cherokee 4.0. I beieve it has anti-lock brakes. When I come to a stop it feels like weight is shifting forward and I feel sort of like a clunk. It doesn't happen every time I stop so ot os kind of intermittent. It only happens when the Jeep is in "Drive", when I put it into "neutral" it doesn't happen. Could this be a caliper problem or a speed sensor problem or???? Any ideas? Thanks!