A transmission assembly for a human- and/or motor-powered vehicle, including a hollow transfer shaft, first and second inner one-way needle bearings, the first inner one-way needle bearing disposed within a first hollow end of the transfer shaft, and the second inner one-way needle bearing disposed within a second hollow end of the transfer shaft; and a first and a second outer two-way needle bearings, each having an inner diameter and an outer diameter, the first outer two-way needle bearing disposed about the outer diameter of the transfer shaft near the first hollow end of the transfer shaft, and the second outer two-way needle bearing disposed about the outer diameter of the transfer shaft near the second end of the transfer shaft, such that the inner diameter of each of the first and second outer two-way needle bearings contacts the outer diameter of the transfer shaft.