I have an 98 Expedition w/ auto transmission (not 4 X 4) I need to know what specific type tranny fluid to use?

OH.. and by the way its a 5.4 liter engine..

4r70w... MerconV fluid
4r100... MerconIII

MerconV is a safe replacement for any older trans as long as you are sure you will never add MerconIII again. That doesn't mean that MerconV will fix whatever problem you might be having at the time. It just means that you cannot put MerconIII in again. For reasons I don't understand, (probably corporate greed), they are compatible in only one direction. III to V but not reversed.

Some newer models require different fluids that I've personally noticed changes in color, consistency and smell. Any car or truck '03 or above you should pay close attention to whats needed.