Complex sentence: If the half shafts are not identical in length the longer one is generally constructed thicker than the shorter one or one axle may be solid and the other hollow this allows for the wheel to turn at the same rate while under the engine power.
Split into simpler sentences: If the half shafts are not identical in length the longer one is generally constructed thicker than the shorter one or one axle may be solid and the other hollow. This allows for the wheel to turn at the same rate while under the engine power.