Abstract: A sprocket wheel and control mechanism for a chain or belt drive transmission with a continuously adjustable mechanical advantage has diametrically opposed sprocket, spur and/or friction gears offset from the center of the sprocket wheel. Piston and cylinder assemblies are used to position the sprocket, spur and/or friction gears. There is a mechanism for equalizing the distance from the axis of the sprocket wheel of the sprocket, spur and/or friction gears, the equalizing mechanism using a collection of linear linkage guides such as telescoping sleeves and rods, or a series of intermeshed gears connecting toothed shafts in the manner of a rack and pinion. A valve regulates the hydraulic fluid to the piston and cylinder assemblies on the sprocket wheel.