[basketcase]

Someone may have in the past and rust could be holding it partially applied. Check to be sure they are fully released.

Jack up the rear and see how hard it is to turn the wheels when they are cold. There should not be a noticeable drag but just a slight brushing sound as they turn is ok. Then get in your truck and press the brake pedal a few times and check to see if the drag has increased afterward. If it has that tells you that the shoes are not retracting properly after you let off the brake pedal.