When I rebuild a diff, I take some time and "sneak-up" on the right tension. What I mean is, as I put it together, and start to tighten the diff nut, right when it makes the diff come together, I start turning the wheels making the diff operate. (tires move in opposite direction) I'll do this for about 30-seconds to a minute. Then I'll tighten it up a little more, turn the wheels again. I keep doing thiss till I have what I think is the right amount of pressure on the diff. I was "TOLD" that it's possible to "dent" the diff balls or the diff rings if you just tighten the diff all the way all at once. Weather that is true or not, I don't know, but my diffs go together pretty smooth. Hope this helps.