Originally Posted by 89newbie

Bear with me im going to explain this to you, in depth so you understand rear brakes. Motion combined with worn parts cause this. Here is the deal on old brakes. WHen you are going foreward the brakes shoes shift to a position that might be refered to as down, in other words the shoes move ever so slightly from that foreward drag. Actually the front pin that holds them in place drops down and the rear pin rises, that allows the shoes to travel so slightly. When you go in reverse, the front pin rises and the rear drops. Next thing to know over turned drums contact on the bottom of the shoe and the top of the shoe, with no contact on the shoe center. Finally the shift of the shoes from the pins allowing movement that allows the emergency brake lever to drop down, in direction when in reverse, allowing the tension on the bar that expands the brake to loosen so slightly, and that can relax the shoe tension slightly, which results in reverse vehicle creep. Self adjusters adjust thihter when you back up from this movement which causes the paw attached to the bar to tighten the brakes. Back to worn or over turned drums. If the drums have been turned beyond limits contact surface area becomes on the top and the bottom of the shoe, without full contact at the centers. The good news is you may be able to get the brakes tighter by backing up and appying the brakes several times hard and get it to adjust more so it keeps the truck from moving when e. brake is on and you go into reverse. Bad news is when we have this situation we need to rebuild rear brakes, which includes drum checks for size and condition. A new rebuild with poor drums will result in poor shoe wear in combination with cracks in the center of the shoe area from dis-proportunate shoe contact, which is the result of overheat on the areas that are actually contacting.

Originally Posted by Siwon

Thanks, that clears things up.

Since I already want new brakes, what do I buy for the drum brakes? Are mine 9" or 10"?

Autozone shows:

Brake Drum - Rear
Brake Drum All-In-One Kit - Rear
Brake Drum Self-Adjusting Kit-Rear
Brake Shoes - Rear

and there's also the wheel cylinder.. what all should I get?

I'll be getting the front brake pads and rotors done at the same time.