Engine brake for offroad vehicle

摘要

An engine brake for a vehicle having a frame rollably supported by at least one wheel, an engine supported by the frame and having an output shaft, the output shaft arranged to drive at least one wheel supporting the vehicle through a transmission, is disclosed. The transmission has a drive pulley driven by the output shaft and a driven pulley driven by the drive pulley. The drive pulley comprises a fixed sheave and a moveable sheave moveable relative to the fixed sheave. The moveable sheave in a first position relative to the fixed sheave causes the drive pulley to drive the driven pulley in a high speed position and the moveable sheave in a second position relative to the fixed sheave causing the drive pulley to drive the driven pulley in a low speed position. The engine brake comprises an air chamber defined in part by the moveable sheave and a vacuum apparatus removing air from the chamber and moving the moveable sheave to its second position when a speed of the engine is reduced.