leaky auto hub seals...they are not that easy to replace...they can be installed without the special tool, but it can be quite a PITA..
If it were my truck, I would plug off the hoses and use the hubs manually if yours have that option, or install manual hubs...the auto hubs cause a lot of grief.......i know the work great when they work, but when they fail, they suck in contaminants, water etc into your hub area...I prefer manual...and a lever in the cab too..