I have a 2000 Frontier Crewcab 4wd with high mileage [174k]. Any recommendations on fluids to use to renew the gearboxes [tranny, ft diff, transfer case, rr diff]?

Do a search...this question comes up every couple weeks.80WI'll asnwer one more time....you didn't say if your truck was a manual or auto.

I'll address a manual: GL4 and GL4 only should be used in the transmission (not anything that says it's a replacement for all GL levels, and not your standard gear oil). Napa sells it in 2qt jugs, or if you want full synthetic, go to your local Dodge dealer and ask for 6 quarts of NV4500 transmission oil. That's a full synthetic GL4 made by Castrol.

For diffs and Tcase, standard 75W90 or 80W90 GL5 is fine. Synthetics are better.