Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
It sure has all the symptoms of wet brake shoes. Was it by chance parked in any water?
Were the rear brake shoes replaced?
As long as there is no signs of any brake fluid or gear oil from a leaking axle seal that has leaked onto the brake shoes, it is most likely a master cylinder issue. You would need to pull the rear wheels off and inspect the brake shoes to confirm they are dry before replacing the master cylinder.