On my 95 k2500 the rear brakes howl when when the petal is applied. And the parking brake seems to stick on when it is cool out. When i drive about 20 feet i can hear and feel the shoes release. When I got the truck I had them looked at due to the parking brake not working. They replaced the shoes drums hardware kit wheel cylinders and the cables. After new parts they started doing this and one side would lock up. Took it back in and they said a wheel seal was leaking but the shoes where ok. they replaced the seals and still had the problem. took it to a different shop and they said the other side was leaking and replaced it. They said everything was ok. Well it is not. Ive never been good with drum brakes but I am tired of heaing them when I apply the brake so i might dive into them. The only thing that isn't new back there is the backing plates. Could these be warped and causing this?