The Nissan Path

Have had my R51 about 5yrs now and has 130k on her. I've never changed the diff fluid or transmission fluid and was wondering if I should. Did the trans cooler bypass when I first got it and never messed with the trans since. I have no issues with the trans or diffs so should I leave the trans filter and fluid alone (fluids good, unburnt, not terribly dirty). Thanks.

I would change them out. And don't forget the t-case fluid (which is the same as the ATF).
For transmission and t-case, I used Valvoline Maxlife ATF (drain and re-fill).
For the rear diff, 75w90 synthetic and 80w90 (although I believe you can use 75w90 too) for the fronts.

Folks around here generally do 30k-50k drain and refill intervals for the ATF, front and rear diffs.
If you plan to keep the truck for a while, I would certainly change the fluids out.

easy to do and cheap insurance. Go for it!

The trans doesn't have a "filter," just a screen. I would just do a drain and fill; I usually do one around 50-60 thousand miles. It'll take about a gallon of ATF, a crush washer for the drain plug (same as the one for the engine oil pan: Nissan 11026-01M02) and the drain plug toque spec is 25 lb-ft. I also use Valvoline Maxlife Full-synthetic ATF which I get at Walmart for about $18 for a 1-gal jug. I also use the Maxlife for the transfer case, but the capacity will vary depending on whether you have the standard transfer case or the "AUTO-mode" case. I use Mobil One 75W90 synthetic gear oil in the front and rear diffs and you'll need a 10mm hex socket for the drain and fill plugs on the transfer case and diffs. Torque is still 25 lb-ft but the drain and fill plug crush washers are Nissan 11026-4N200.

Sorry haven't been on in awhile. Thank you to who all responded. Il be doing all that before winter!

I just did my transmission and full driveline a couple days ago, before driving from CA to VA. I'm not really worried about differential oil going bad, but...let's just say it made more of a difference than I thought it would, between shifting, smoothness, and the oomph in "crawl" from a standstill in drive.

I just did my first rear differential fluid change at 257,000 miles. Fluid did not look so bad but it did have a lot of metal shavings and the magnet was full of shavings and sludge. I used used AMALIE ELIXIR full synthetic 75W90 for $8 a quart ...so far so good cant be that!