You use ATF in the tranny in most cases. Get under the car and look for a sticker near the bottom of the bellhousing. It is usually covered in dirt and PVC coating that you'll need to scrape off. It will either be orange and say ATF only, or be green and say somethign else. Check that first, but 95% of the time it uses ATF.
You may as well to the differential while you are at it. That I use 75-W90 in, non-hypoid I believe. You'll need a big allen wrench for that (like 14mm?), some clear tubing and a funnel. It is a PITA, but a good idea.