Transmission (10) comprising a sun (1), a planet carrier (4), a first planet (21) having a first axis of revolution (41) and a first lateral surface (31) that is nonparallel to it, and a ring (3). When there is a relative movement between said first planet (21) and said ring (3) for a constant transmission ratio, a force of power transmission, Formula (I), between said first planet (21) and said ring (3) defines a plane (55). The transmission (10) comprises rolling means (15) for allowing a movement of translation between said ring (3) and said first planet (21) along a direction of translation (65) that is perpendicular to said plane (55) such that different transmission ratios can be obtained, corresponding to different coupling points (8) between said first lateral surface (31) and said ring (3) along said direction of translation (65).
