I have a 2007 C6 coupe auto w/ 25K miles. It has the original brakes w/ approx 50% wear. When I come to a complete stop and release the brake I hear a grunt sound. It does not happen any other time and if I try to recreate the sound by braking and releasing it won't do it

Any ideas suggestions?

Thanks in advance.

 

Are you sure it's 50%? The pads can wear at an angle.