1998 ford ranger rear drum brake problems

I own 1998 ford ranger 4x4 Super Cab, 4.0 liter V6, 124000. I recently rebuilt the rear drum brakes with parts from advanced auto. The brakes then worked OK I had the truck in the local repair shop for unrelated issue and the guy told me I had the wrong size rear wheel cylinders installed. I approved him to put the correct ones on. Now when I reverse in the morning to back from the driveay the rear brakes make an awful noise and lock up especially on damp or rainy days. They tend to grab or lock up the first few times applied in the forward direction, then they are OK.
Any ideas??