Abstract: A transmission is provided which includes a fixed housing or support, an input part moveable relative to the support and a torque shaft, a first one-way clutch between the torque shaft and the driven shaft, linkage elements rotatable about the axis of rotation of the driven shaft under the influence of the input parts and an inertial body mounted on the linkage elements to be cyclically angularly deflected in response to the input part, the reaction forces generated by the inertial body as it cyclically deflected being applied to the torque shaft as a positive and negative torque and the torque shaft being connected over a second one-way clutch opposite to the first one-way clutch either to the support or to the driven shaft over a rotation reversal system whereby the driven shaft can be rotated by the torque shaft in one sense of rotation only.