As said above, they tend to wear fairly quickly. If you can, take it apart now and check out the clutches and the side gears. Look for wear on the side gear splines, and look for wear where the Belleville washer rides. Because all the pressure rides on that contact surface, thats where you will see the most wear.
They are kind of tricky the first time through one, but it's just time. You can make all the tools they list, you shouldn't have to buy any tools to rebuild one of these.
http://www2.dana.com/pdf/5313-3.pdf