Remixed Differential from Thing-O-Fun. I added the Yoke to make it more realistic. The original files had a lot of play and were not all consistent sizes which are now consistent. I also redesigned the spider gears to accept screws from the outside to allow 4 spider gears to be installed.
I added a stand with a motor from here http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_2128219_-1. Use the 2 spur gears to drive the entire assembly. Motor can be wired to a USB port.
Input Pinion (1)
Side Gear_V2 (2)
Spider Shaft_V2 (2)
Top (3) (or you can print another 2 for the Yoke)