1996 Chevy Tahoe squeaks in reverse

My chevy tahoe keeps squeaking in reverse. I took it into the shop and they said it was my front rotors and pads being very low causing the squeaking sound. I got them replaced and my car still squeaks in reverse. I was thinking it's the shoes and I got them checked out and they said the shoes were fine but that my rear brakes need cleaning. I got them cleaned and the car still squeaks in reverse. The sound seems to be coming from the left rear tire. My emergency brake doesn't work. Does that have anything to do with the squeaking?