Hey Cam, What's the theory behind the 10w30 in there to reduce the gear noise?
Create a bit of wear to match gear faces up?

I have a 4.10 9-bolt running used OEM gears that have a whine on the drive side that I can't get to go away with the set-up..

Yep. Machine by punishment!!! You just cant do it very long. In the old days there were all kinds of cockamaymee scams to "sell it quick" by filling the diff up with sawdust and another classic was put 3 whole bananas in the pumpkin and it quiets it down but only briefly.... then boom. So in the essence of wanting to keep one going for a while you can try the 10w30 trick but dont blame me if shes already cooked and blows up. This wont do any bad parts any good it just might quiet down a noisy gear seat thats otherwise fine

If it doubt? Change it out

I think the pinion has slight wear on it and I'm getting a dual pattern on the drive side, hence the noise. If I move it around the pattern is too far out of place, and the coast side goes off.
Visually the gears look great. Might be worth a shot... I'm not worried at all about it blowing up, they've been like that for a few years now.

A lot of third/fourth gen diffs are not ture anymore after years of abuse from the torque arm bending the hell out of the pinion area so sometimes your doomed before you start.

In my experience pattern is not so crucial as backlash and pinion depth. But even a perfectly well set up diff can sometimes whine its just harmonics it wont hurt anything aside from your NVH ( noise, vibration, harshness ) factor. About one in ten diffs I set up seem to be noisy no matter what happens but they usually mellow out after 10-20K or so. Most of them are DEAD silent right from the get go like mine used to be but its starting to make a bit of noise now. Same gear set through three engines, two transmissions, and 8 years of pounding though. Only problem i ever had was grenading a Torsen T2R ( man that thing was sweeeeeet while it lasted ) but im back to the tried and true T-Loc

interesting

not to be nitpick but the 9 bolt has 4.11 gears