Sometimes when I am backing out and I hit the brake to put the car in 1st I hear this really loud ERRRRR! It happens for a while and goes away and then it does it again. Has anyone else experienced this?

Yep mine does it too. If I'm on a steep incline only though. No ill effects just a loud hollowish noise.

More than likely is the rear pads cooling onto the rotors and sticking a little. Once you get moving forward they should brake loose. If you don't feel any ill effects while braking and no unusual fast brake wear. DOn't worry about it.

-Andy

Usually happens for me when I first back out of the driveway in the morning. I always said it was just cold sticky brakes because it never happens as soon as I start moving, and it doesn't happen in the summer. Jared.