Abstract: Acontinuous gear change mechanism which includes an input shaft, an output shaft, interlocking cogged wheels, a hydrostatic transmission and a epicycloidal gear.The hydrostatic transmission includes both a hydraulic pump and a motor being at least one of these components of the hydrostatic transmission in gear with one of the epicycloidal gear components.Two other components of this epicycloidal gear interlock with separate and independent portions of the input shaft.At least, in addition, the pump is of variable-flow type and is reversible in its operation.