Alright, I believe you either have the shoes on incorrectly or bad brake shoe material. See the illustration below, there are two shows for each side...the primary and the secondary. The primary is #29 in the picture, it always goes on the side closer to the front of the car, it also has less material at the top near the wheel cylinder...this helps the shoe not to grab the drum. The shoes are all identical and can be easily switched around. I've opened new packages with all primary's in there or all secondaries, so if you don't do rear brakes often, you wouldn't even realize this. Check the shoes, if they're incorrect, turn them around...if they look fine, try another set and return these...also be sure no brake fluid/grease is contacting the shoes this will also cause them to grab, and use the illustration to double check the hardware was installed properly. If one spring is backwards it'll cause grabbing as well.