[PeteKz]

That's bit too much marking compound for me, but it indicates that the pattern is about the center of the drive face of the ring gear. I don't think you can do much better than that, and if you keep messing with it, you might end up worse.

As for those perfect long-oval shaped contact patches in the books, I've not had much luck achieving them, but all my R&P experience is on American iron and British scrap iron. I haven't done a 915 yet. So if Matt has different guidance, listen to him.

Another thing I've found is that if the R&P run quietly, leave the mesh adjustments alone. I've had the experience of setting up a Ford 9" diff so the pattern and lash were within tolerances, but it then made more whining than before I adjusted those clearances. It quieted back down after a few thousand miles, but if yours was quiet before, be conservative about changing it. Mercedes used to set up their diffs at the factory by running them and measuring for minimum noise, then marking the ring and pinion adjustments to .01mm. To set up those diffs required a special jig that allowed the factory measurements to be duplicated, but only a very few shops had access to those. That's sort of the extreme case of German precision, but at least MB thought it was the right way to do things.