Help with Leak

[gmtahoe02]

I have a wierd leak on my 2002 Z71 tahoe. Its coming from a little black cylinder attached to a small rubber hose that leads down, i haven't gotten under to see where down is yet. But the little black cylinder is at the end of the hose and that is what is leaking. It is just resting against the wheel well right near the bottom of the batter on the drivers side. It appears to be oil. I am not sure even what it is. Just started yesterday. Here are the pictures i am talking about. Looks like it might be an easy fix, but my curiosity wants to know WTF it is more then anything. Any help would be great. Thanks to all.

 

[Sepiroth]

That is the vent hose for your front differential unit. Nothing to worry about, that is unless you dont have a 4x4 and in that case, I dont know what that hose is.

 

[gmtahoe02]

It is 4x4 but its leaking out that hose pretty good so i'll have to take a look at why its leaking from there then. Something is forcing that fluid out the vent.

 

[Sepiroth]

If you had the 4x4 system checked and fluids flushed, it might be overfull