leaking fluid from rear end on 2001 Lincoln Navigator

Why would liquid be leaking from the rear end? Its not alot, but I am concerned. Is it a gasket? I am going on a trip and need to know ASAP, Thanks!

Asked by for the 2001 Lincoln Navigator
The liquid could be brake fluid ( Clear or semi clear ) or gear oil either way you need a shop to check this before the trip because you could loose braking or damage the rear end ( very expensive ) and you can locate a shop near you here