More than likely its a bad seal, the worst part of changing it is getting the yoke off, the nut is supposed to be 200 ft/lbs if I can recall, and sometimes it's take a puller to remove it. I think I was able to use a harmonic balancer puller. (again, it's been a few years) The seal just pops out. Maybe someone else will chime in with a seal part number. One more thing, try to move the yoke up and down to check for play before you loosen the nut, just to check for bad pinon bearings.
Edit: looks like garage gnome posted while I was typing
Dang kids these days!!! [smiley=s11724.gif]