Based on the multiple reports of low filled rear diffs, I'm going to change my rear diff next week. I'll use Mobil 1 75w90, just like I did with the 2007 Hemi. (It'll give me the assurance it's correctly filled, AND it'll drain out the swarf and any other break-in contaminants.)
I have nothing against Valvoline: I've just used Mobil 1 and never been let down.
(Edited to add: I just caught that this is a in the Hemi thread, and I've got the baby diesel. My 75w90 is spec'ed for my 3.21 diff. The 3.92 should use 75w140, FWIW.)