[suicideneil]

It's not noise you should be looking for really, its much more about feel & smoothness.
Ideally the pinion gear shouldnt be able to move in or out more than a fraction- it shouldnt bind however as you rotate it / the ring gear once assembled. Likewise, the ring gear / output shafts shouldnt be able to move in or out ( side to side ) more than a fraction.

Every diff is different due to maching tolerances but a few 0.2mm shims hear and there should do the trick; so long as the diff roates smoothly and doesnt bind or have excessive play, you'll be fine :)