Changed the front a rear diff oil and the t case fluid in my xterra today. Dealer claimed it was all done when I bought it but I'm always skeptical of these things. So 15k since I bought it and it was looking really good so I tend to believe that they actually did. 115k on the truck and everything looked absolutely perfect, just a smudge of black grime on the magnets. I'll bump these fluid changes to around 20k now, nissan recommends 30k but it is easy enough and with lots of hot weather and heavy loads/off road driving it is not gonna hurt anything to keep doing it alittle early. Put lucas gear oil in the specified weights in the diffs and royal purple max atf in the t case. Definitely faster shifts in and out of 4x4 now.