[Yuille36]

I just did this a few months, your rear differential has three fill plugs and three drain plugs. The outside chambers use 75w140 and center section uses 75w90.
I would recommend purchasing ECS Tuning, magnetic drain plugs, you only need three. These same drain plugs work on the transfer case and front diff.
If your going to change your rear differential fluid, I recommend that you also change the front diff and your transfer case. I also wrote up a post of this already with photos.