Drum Brake System: Description and Operation

This drum brake assembly is a duo-servo design. In the duo-servo brake, the force which the wheel cylinder applies to the primary shoe is multiplied by the primary lining friction. This applies a large force to the secondary shoe. Torque from the brake shoes is transferred to the anchor pin, through the backing plate and to the axle flange. Adjustment for both the primary and the secondary shoe and linings is automatic during reverse brake operations.

Important:
^ Install all new components included in the repair kit used to service the drum brakes.
^ Lubricate the parts (6, 7, 12, 18, 21 23, 24) as specified.
^ Do not use lubricated compressed air on brake parts as damage to the rubber components may result.
^ If any hydraulic component is removed or disconnected, you must bleed all or part of the brake system.
^ Replace the shoe and the linings (17 and 29) in axle sets only.
^ The fastener tightening specifications are for dry, unlubricated fasteners.
^ Perform service operations on a clean bench, free from all mineral oil materials.