What is the recommended aftermarket tranny and rear difference fluid? Under the hood, it specify the use of Nissan type-D fluid ONLY! It also specify that the use of Nissan type-J or any other fluid will damage the transmission. Is the tranny that sensitive?

The Armada takes Matic J or Matic S for the late models, not Matic D.

Is there any aftermarket equivalent, say from Mobil1? Would Mobil1 be better or is the dealership product the best?

I've heard rumors that other stuff is compatible, but I would not risk any warranties on a substitute fluid in the transmission.

As far as the rearend goes, I'm pretty sure it's 75w85 or 75w90 full synthetic, which is available anywhere. We have customers at our dealership who do a lot of towing that have switched to 75w140 because it is less likely to boil under the extreme conditions they subject their trucks to.

In case anyone is interested, the official "brand" for the diff fluid is not Nissan-specific. See below from our parts expert (none other than Joe):

"The diff. weight is 80W90. The factory “brand” is actually Pennzoil believe it or not…"