Abstract: A replacement assembly is provided for retrofitting old, discontinued, mechanically-operated, low-drive, Caterpillar sidebooms with a hydraulically-operated fail-safe sideboom system. Conversion of discontinued, mechanically-operated, low-drive, Caterpillar sidebooms is accomplished by replacing the entire existing mechanical assembly with a single frame-mounted hydraulic assembly comprising a boom winch, a load winch, and preferably a single hand-operated joystick control. This single frame assembly is configured to be received by the existing foundation on discontinued Caterpillar sidebooms. Joystick technology is provided which negates cumbersome clutches and related multiple controls by affording a sideboom operator the ability to completely control the functions of both the boom and the load with a single joystick control which replaces the six conventional hand-operated mechanical controls that exist on the discontinued Caterpillar sidebooms.