2007 Vibe grinding noise

16k miles, AT, grinding noise occurs while braking. All rotors and brakes are like new. I lifted up the car and put in D, then i gently pushed on brake. Drivers side wheel stops but passenger side is still going. Push brake down further and the passenger side finally stops, but during this harder push on the brake, is where i hear the grinding. It is all quiet at the rotors and sounds like it is trans/axle related. I jsut want to figure it out before i take it back to dealer to look at. Any thoughts?