what fluids need changing?

Hey guys, can someone tell me what the best fluids are for replacement in the differentials? Also, does the transfer case have its own fluid changing method?

So basically, what type of fluid should I use and what is the process of changing it?

Thanks

I just realized that this is in the wrong forum. Sorry

Well since you haven't posted in another section, perhaps you've already found the answer. If not, the backyard mechanic would be the place to look. This is what you're looking for:
http://mywebpages.comcast.net/xterra/tech/Diff_fluid_change.txt
It covers the diffs and the transfer case.

Thanks a lot. I actually hadn't found the info anywhere else, but that link is exactly what I was looking for.