Parking Brake System: Description and Operation

GENERAL DESCRIPTION
There are three basic types of parking brakes used. The lower GVW models use leading/trailing rear drum brakes. The higher GVW models use duo-servo rear drum brakes. The highest GVW model C3500HD has a propeller shaft parking brake mounted on the transmission.

LEVER
The parking brake lever is located on the left side of the driver's compartment and is activated by foot pressure. The lever assembly has a ratchet mechanism in it to allow varying degrees of parking brake application. The parking brake handle on the instrument panel allows the driver to release the parking brake.

CABLE SYSTEM
The cable system will vary depending on the type of parking brake system used. Models with rear drum brakes use a system that includes one front cable and two rear cables. The front cable connects to the lever on one end and the equalizer on the other end. The rear cables attach to the equalizer on one end and the parking brake struts in the drum brakes on the other end.

Models with a propeller shaft parking brake use a one-cable system. The cable connects to the front lever on one end and the rear lever on the other end.

BRAKE LAMP
The BRAKE warning lamp on the instrument cluster turns on when the parking brake is applied. The lamp can also be fumed on by the switch in the combination valve and the antilock brake system.

PARKING BRAKE SWITCH
The parking brake switch is located on the lever assembly. The switch serves as the device to turn on the BRAKE lamp when the parking brake is applied and turn it off when the parking brake is released.

DAYTIME RUNNING LIGHTS
All vehicles are equipped with a daytime running light (DRL) system. This system uses the parking brake switch to turn the headlamps off when the ignition switch is ON and the parking brake is applied. For more information on DRL, refer to Daytime Running Lamps Module and Diode Module Replacement in Lighting Systems.