Thanks for the replies. I bought the truck, 2001 Expedition Eddie Bauer with 38k miles for the wife and kids. She drives about 7500 or less miles a year so I figured it should last her a long time. It now has 52k miles.

The truck has the 5.4 liter engine and is always in AWD mode, or it can be put into 4WD High or 4WD Low. It is possible the fluid could be wrong, I will replace it and the filter immediately for preventative maintenance and see what happens.

Thanks again