8-3/4 Noise After Rebuild..What's Normal??

I installed a Auburn limited slip differential in my truck awhile back with 4.56 gears. Auburn gear says point blank no synthetic blend of gear oil of any kind it will void the warranty. I used the dino 90w. I put 500 miles on it and then changed the oil. Some drive it longer and shorter periods of time before they change it. I added Mopar limited slip additive and it has been fine ever since. I have no gear noise at all. You shouldn't either but I did change the gears out on a 8 3/4 that was in a Charger I had and it made a little noise on deceleration. But I mean it was just barely noticeable and I just lived with it. I believe it was better to use dino 90 in the break in period myself and go with synthetic. But Auburn gear is against it period for some reason.

I used Motive gears in my truck and Yukon in the Charger. I have always heard that Yukon are noisy.