GM 15679733
Drum

Test the brake drum diameter first with a micrometer; proceed to replace the piece fully when the measurement reaches above its refinish limits. When extreme scoring meets brake pulsation criteria you need J 41013 rotor resurfacing kit (J 41013) to eliminate all rust from brake drum flange thoroughly. Follow brake lathe maker guidelines to refinish the brake drum to get its optimal stopping quality against potential braking problems. When machining is complete apply 120 grit aluminum oxide sandpaper to make an even braking surface and wash the surface clean by using GM P/N 12377981 (12377981) or a matching alternative cleaning fluid.

Clean rust from the brake drum flange using J41013 Rotor/Drum Flange Resurfacing Kit J41013. Restore the brake drum only when scoring is severe plus you spot brake pulsation or corrosion beyond the braking surface depth. There is no need to honor the drum since it requires replacement if the largest measurement exceeds the refinish limit using a micrometer. Make a non-directional braking surface on the finished part with regular aluminum oxide sandpaper at 120 grit. Use brake parts cleaner GM P/N 12377981 (12377981) or an equivalent to cleanse the braking surfaces before further repairs. Tighten wheel nuts with equal force to the correct specifications to stop brake vibrations which damage rotors.

Take off the rear brake drum from the vehicle.