A carrier shaft set, comprising: an input carrier shaft portion having an input carrier shaft portion axis defined between a planetary gear set end and an input shaft end, the input shaft end having an outer surface, the input carrier shaft portion comprising a wedge-shaped member having an edge and an outer edge that defines a taper region relative to the edge of the wedge-shaped member; characterised in that a ratio of a length defined between the input carrier shaft portion axis and the outer edge to the outer surface of the input shaft end is between 1.23 and 1.30; and a carrier shaft portion having a carrier shaft portion axis defined between a planetary gear set end and a shaft end, the carrier shaft portion comprising a shaft portion having an outer surface and a wedge-shaped member having an edge and an outer edge that defines a taper region relative to the edge of the wedge-shaped member, wherein a ratio of a length defined between the carrier shaft portion axis and the outer edge to the outer surface of the shaft portion is between 1.23 and 1.30; and characterized in that the wedge-shaped member of the input carrier shaft portion further comprises a wider wedge portion and a narrower wedge portion, the wedge-shaped member of the carrier shaft portion further comprises a wider wedge portion and a narrower wedge portion, the wider wedge portion of the input carrier shaft portion is axially aligned with the narrower wedge portion of the carrier shaft portion, and the wider wedge portion of the carrier shaft portion is axially aligned with the narrower wedge portion of the input carrier shaft portion. an input carrier shaft portion having an input carrier shaft portion axis defined between a planetary gear set end and an input shaft end, the input shaft end having an outer surface, the input carrier shaft portion comprising a wedge-shaped member having an edge and an outer edge that defines a taper region relative to the edge of the wedge-shaped member; characterised in that a ratio of a length defined between the input carrier shaft portion axis and the outer edge to the outer surface of the input shaft end is between 1.23 and 1.30; and a carrier shaft portion having a carrier shaft portion axis defined between a planetary gear set end and a shaft end, the carrier shaft portion comprising a shaft portion having an outer surface and a wedge-shaped member having an edge and an outer edge that defines a taper region relative to the edge of the wedge-shaped member, wherein a ratio of a length defined between the carrier shaft portion axis and the outer edge to the outer surface of the shaft portion is between 1.23 and 1.30; and characterized in that the wedge-shaped member of the input carrier shaft portion further comprises a wider wedge portion and a narrower wedge portion, the wedge-shaped member of the carrier shaft portion further comprises a wider wedge portion and a narrower wedge portion, the wider wedge portion of the input carrier shaft portion is axially aligned with the narrower wedge portion of the carrier shaft portion, and the wider wedge portion of the carrier shaft portion is axially aligned with the narrower wedge portion of the input carrier shaft portion.