Question about 06 F-150 rear end?

I just noticed that I have a hose that is hanging loose from my rear axle. It is about 18" long and connects directly into the rear axle. There are also 2 other lines (tubing about 1/8"dia.) that go to each wheel. The loose hose is rubber and has oil or grease on the loose end. I can not see anywhere that it could connect, but know it goes somewhere.