Some GM W-Body vehicles covered by this guide use an advanced leading/trailing shoe design drum brake on the rear wheels. The parts count is greatly reduced and the operation and servicing is designed to be simpler than other drum brake designs.
The rear drum brake used on some of the W-Body vehicles uses a single universal spring to hold both the shoe and lining assemblies to the backing plate and also acts as the retractor spring for both brake shoes. Force from the brake shoes is transferred through the fixed anchor and backing plate to the axle flange. Adjustment is automatic and occurs on any service brake application.
Please note that with this design, it is normal for the leading (front) shoe to wear at a faster rate than the trailing (rear) shoe. Do not switch the position of the brake shoes that have been in service as this may render the self-adjustment feature inoperative and may result in increased pedal travel.