I've got 65k on my 2001 X. I've kept up on most of the normal maintenance, doing it all myself (great idea - learned quite abit about the truck). I have not had the diffs, the transfer case fluid, or the manual transmission fluid changed. Nissan seems to recommend this around 60k, but I've heard (here and elsewhere) that with these fluids it's best to change every 30k or so and if you don't it's best to leave the current fluids in there as the accumulated gunk can damage parts if the fluids are changed.

Is this correct? Is 65k or so an appropiate place to change these fluids for the first time? Or is that true of some of these and not the others? Thanks so much and please excuse my ignorance.

Nissan recommends the diff be changed every 30k, so you're long overdue. If you tow anything or do any off-roading, 15k is the recommended interval for all of them.

This is all covered in your Owners Manual.

Yeah, I know I'm overdue.

My question is, since I'm so overdue, is it still a good idea to change those fluids? I know I've heard from multiple places that you get a buildup of crap in these places (especially the diffs) and if you miss the 30k interval, change at 60k can cause more problems than just leaving the original fluids due to stirring up that crap during the flush. Any truth to that?

For an autoamtic transmission, yes, varnish can build up and a fluid change will put fresh detergent in there which can cause the varnish to come loose and gum up the works.

Luckily none of that applies to a diff or a manual transmission - so change those fluids!! While you are going through the trouble, you might want to switch to synthetic - I will.

And since it's been so long on your diff, I would probably do it again in 5K, until the fluid starting coming out somewhat clean. My first Miata had 90K on it and the diff had never been changed - it came out like sludge. It took a few back to back changes to clean the stuff out

I know this is old but....

http://findarticles.com/p/articles/mi_qn4155/is_20070830/ai_n19504255