Sounds like your diff is probably rebuilt incorrectly.

Here's a link on how to rebuild a ball diff:
http://www.balakracing.com/diffmaintenance.htm

It doesn't tell you what parts go where, but it does give a nice step by step plan on how to do it. The manuals show what part goes where, but i'm not sure if the orientation of the parts is critical (which way they face).

I haven't rebuilt my diff yet, but i plan to do it soon, so i have been looking into it.