Summary

Working Model of an open differential with a stand to hold it together. Easy to print - requires no or minimal support material (I didn't use any)

Instructions

Requires about 35 3x8mm flat-head screws. Up to 3x12mm should work as long as they are flat-head or "countersunk". I prefer hex drive like these:
http://www.mcmaster.com/#92125a128/=ynqmb3
Or check eBay

The leading number in each filename indicates how many of that file to print.
The spacer goes around "axle_holder_right". Print a second if there is still too much play.

I made the through-holes 3.6mm and the threading holes 3.1mm because the printer/slicer I'm using under-sizes the holes.
I recommend a test print of "pinion_spindle" first and attempt to thread the 3mm screw to make sure it works. If the holes are too loose, you can try 6-32 x 3/8" flat head like this, they are slightly larger:
http://www.mcmaster.com/#92210a146/=ynrikz

Easy to print differential (no support material)