My expedition doesn't have a problem in the rain...just have good tires and you should be fine. Even if you don't have good tires, if sliding is a problem, drop in into 4x4 high range. I have 3 inches of snow on the ground right now...expedition doesn't even know what snow is! ;)
The 2010 Ford Expedition has rear wheel drive.
The 2004 Ford Expedition has rear wheel drive.
The 2001 Ford Expedition has rear wheel drive.
The 2006 Ford Expedition has rear wheel drive.
The 2005 Ford Expedition has rear wheel drive.
The 2011 Ford Expedition has rear wheel drive.
The 2002 Ford Expedition has rear wheel drive.
The 2014 Ford Expedition has rear wheel drive.
The 2012 Ford Expedition has rear wheel drive.
The 2008 Ford Expedition has rear wheel drive.
The 2013 Ford Expedition has rear wheel drive.
The 2007 Ford Expedition has rear wheel drive.