I just replaced the rear brake cylinders on my 79 3/4 Chevy van. Get a couple cans of brake cleaner. Block the front tires. put it in neutral. Don't set the parking brake, don't touch the brakes while you are doing this. jack it up and take off the wheel, and turn the rotor cover to line the hole up with a little gear-wheel. Turn this gear-wheel (the rear brake adjuster) till the cover can be slid off. If it wont come off use a block of wood and a hammer to beat it off. Spray all the asbestos dust off the brakes and look at the springs and pieces. If they look weak, you'll need a spring-kit to replace them. To replace the brake pads, carefully pull all the springs off and remember how they go. Put the new pads on, replace the rotor cover, and tighten the rear-brake adjuster. Do the same thing on the other side, and drive in reverse and fully stop a few times to get the brakes completely adjusted.