GENERAL MOTORS: HYBRID BRAKE NOISE OR VIBRATION. BRAKES GROAN OR THUMP NOISES DURING BRAKING; BRAKE PEDAL PUSHBACK OR VIBRATION THAT MAY RESEMBLE A PULSATION AS THE VEHICLE COMES TO A STOP; A SLIGHT DROP IN THE BRAKE PEDAL WHEN COMING TO A STOP. *PE UPDATED 6/27/11. *PE