Descending grades with trailers can be hazardous and tricky situations, resulting in over heated service and trailer brakes, that leads to brake fade, excessive wear, and costly unwarranted repairs. BD Engine brake has been the industries time proven VARIABLE REGULATING BACK-PRESSURE EXHAUST BRAKE.Controlled by a lighted On/Off toggle switch or optional stick-mounted rocker switch for manual transmissions, the BD brake communicates with the engines electronic idle verification board for quick engagement. Where it mounts: Most vehicle applications will either have BDs turbo-mount design which bolts in place of the factory elbow between the turbo and the exhaust system or the inline design mounts in the exhaust system between the engine and muffler/DPF/cat. The BD Brakes rugged cast-iron housing incorporates BDs exclusive AlumiBronze bushing and positive sealing piston ring, no blind holes for carbon and rust to form, and miles of leak free retarding. Brake valve is actuated by an air cylinder (newer models) or a powerful, three-inch vacuum cylinder (earlier models). The durable air compressor included in later model kits can even be used for other applications, such as air horns, air bags even air-ride fifth wheel hitches it is that tough. Automatic-equipped trucks prior to 2006 require BDs programmable AutoLoc and PressureLoc kits to electronically control torque converter clutch engagement. This addition effectively reduces slippage, resulting in peak retarding performance as well as lower transmission temperatures. All BD Brake kits come complete with the brake, air compressor (where applicable), mounting hardware, port to monitor the brakes retarding performance, complete instructions and most models come with EGT port.