Full traction differential with hybrid gearing

In a full-traction differential that transfers rotational forces from an external power source to a pair of side-gear worms in a gear complex supported in a housing rotationally driven by the external power source, each side-gear worm comprising a plurality of side-gear teeth, the gear complex comprising the side-gear worms rotating about a first axis, each side-gear worm being fixed to a respective one of two output axles received in the housing, at least two sets of paired balance gears, each balance gear of each set being mounted for rotation about an axis substantially perpendicular to the first axis, each balance gear having a pair of spur-gear portions comprising a plurality of spur-gear teeth, spaced apart from a worm-wheel portion comprising a plurality of worm-wheel teeth, each balance gear being in mating engagement with the other balance gear of the pair through the spur-gear portions and in mating engagement with a respective one of the side-gear worms through the worm-wheel portion, wherein the improvement comprises:

• for each pair of side gear teeth and worm-wheel teeth in mating engagement, either the side-gear teeth or the worm-wheel teeth have an involute profile cut with only plunge feed and the other of either the side-gear teeth or worm-wheel teeth are helicoid worms having a plurality of tip and root modifications made by a concave-shaped cutter;
• wherein the side-gear worms have a helix angle equal to or greater than 45°;
• and
• wherein the side-gear worms and the worm-wheel portions provide a gear ratio between 1.5:1 and 2.5:1.