1997 Chevy Monte Carlo Rear grinding noise upon first start

Brakes problem
1997 Chevy Monte Carlo 6 cyl Automatic 114000 miles

I took my 1997 Chevy Monte Carlo in because the brakes were grinding in the rear. The mechanic inspected the brakes, front and back, and determined two cylinders (one on each rear wheel) were leaking fluid. He replaced them, and the problem was solved. However, when I start my car up, and back it up out of my drive way, it grinds and squeaks. I get to the stop sign, stop and it does it again. I drive it for almost a mile, stop and get ready to turn onto the highway and it doesn't do it anymore during the time I drive. I have noticed that the outside past the tire are rusty. My mother said he used to drive the car in dusty areas, so it could be that. Thanks.