Ford Super Duty (1999-2016) :: 2001 - One Loud Bang / Thud In Front Axle Area When In 4 Low

We were using my 2001 7.3 4x4 (automatic, manual lock outs) in 4 low yesterday on dry pavement in an attempt to pull out the remainder of a 6x6 post in concrete. We were working her pretty hard alternating directions of pulling. At one point we heard a loud bang (see also: thud; pop; etc). It seemed at that point that the front axle was no longer functioning in 4wd. We still had the low gearing feel, but at one point I noticed my rear tires trying to slip on the driveway, but fronts didn't appear to be pulling anymore.

Long story short, came in, went to bed, went out this morning and thought I'd jack up the front end and roll the tires in both 'free' and 'lock' to see if the universal joints (yokes?) behind each wheel were spinning or not, depending on whether free or locked in. I noticed on the passenger side a few drops of a clear/light colored fluid that had dripped from behind the dust cover that isn't functioning any longer. The joints worked as they should, based on if it was locked in or not.

I decided to go ahead and put the back axle on jackstands as well and see how it was working when "driving". When in 2wd, rear worked, front was stationary, as it should be. when in 4high, rear spun, front driver spun erratically, nothing from passenger front (where I had seen drip). 4low was same thing - erratic on driver side, at best.

So I know I have front axle/transfer case issues. The question is, with the drip (smells like grease, so I'm assuming its gear oil?) would I be safe to drive it a few days with hubs in free position? I don't want all of the fluid leaking out when I'm driving down the road. I use the truck for work and wouldn't be able to be without it until later in the week or next week. But I also don't want to drive it if it will just make my predicament worse.