Parallel-axis differential

A parallel-axis differential for vehicle, comprising:

• (a) a housing rotationally driven about a rotational axis upon receipt of a rotational torque;
• (b) a pair of side gears rotatably received in said housing and coaxial with said rotational axis, said pair of side gears being connected to end portions of a pair of coaxial output shafts, respectively, said side gears each having a helical teeth portion formed on an outer periphery thereof;
• (c) at least three planetary mechanisms arranged at intervals in a circumferential direction of said housing, said planetary mechanisms each having first and second planetary gears rotatably received in said housing, said first and second planetary gears being parallel to the rotational axis of said housing, said first and second planetary gears each having a helical teeth arrangement formed on an outer periphery thereof, said helical teeth arrangement of said first and second planetary gears meshing with said helical teeth portions of said side gears, respectively, and also meshing with each other, said first planetary gear located forward of said second planetary gear relative to a rotational direction of said housing when the vehicle is traveling forward;
• and
• (d) window openings formed in a peripheral wall of said housing and adapted to allow the passage of lubricant, said window openings being disposed in correspondence with the intervals between said planetary mechanisms, said window openings each having an extension that exposes an outer peripheral surface of said helical teeth arrangement of said first planetary gear, said window openings being separated from said second planetary gears in the circumferential direction.