This reply may be too late, but it?s worth a shot. While I don?t know anything about this particulate axle, here are a few things that I would check:

*Obvious damage
*Spin pinion and, barring the brakes being locked up or jacked, make sure that it turn smoothly.
*Depending on how much I am paying for it, I may ask to pop the cover and take a quick look - knowing that I will take it if there is no obvious damage

Good luck and let us know how it went