CONSUMER WAS TRAVELING ABOUT 15-20MPH, AND VEHICLE WAS STRUCK ON THE REAR DRIVER'S SIDE. REAR PASSENGER'S SIDE SEAT BELT RELEASED, THROWING CHILD TO REAR OF THE CARGO AREA OF TRUCK. CHILD'S LEFT LEG WENT THROUGH THE SIDE WINDOW. DEALER SIDE COULDN'T HELP THE CONSUMER & TO SEND LETTERS TO THE PRESIDENT OF GMC. *AK