Quote:
Here is another picture and diagram of standard 2 spider diff. Note that the diagram below the picture is incorrectly labeled. The arrows in the diagram labeled "side gears" are really pointing to the spider gears. Differential I built high performance and off-road VW's in my past and a 4-spider upgrade was standard practice.
actually the label to the side gears are not spider gears. they are infact side gears (not sure what or if they have a "technical" name). they connect directly to the axle and spin on one axis through the center of the axle/gear.

spider gears rotate on two axis', one through the gear that is perpendicular to the axis and on an axis through the middle of the axle.

im not an expert on this but as far as i know this is right.