Abstract: The invention concerns a device for power transmission, in a vehicle, between a heat engine shaft and a wheel shaft (5). The invention concerns essentially a device (1) for power transmission between a shaft (2) of a heat engine (3) and a shaft (4) of wheels (5). A mechanical assembly (10) mutually connects the shaft (4) of wheels (5), the shaft (2) of the engine (3) and the shafts (8, 9) of two electrical machines (6, 7). This mechanical assembly (10) comprises at least two mutually connected planetary gearsets (49, 50). The invention is characterized in that the two planetary gearsets (49, 50) have a common planet pinion cage (57) and mutually meshing planet pinions (53-56). In another embodiment, the planet pinions (53, 56) of the two gearsets (49, 50) are mutually integral and coaxial.