Noticed today a hose hanging from the left rear next to the shock. Crawled under and the upper end of the hose goes into the support cross bar under the bed. The only place that looks like it might attach is on a brake line tee. the lines come in to each side of the tee and it appears as though the hose may attach to the top of the tee, but there is no nipple. From the dirt on the end of the hose and the dirt on the tee, it may have been unattached for a while.

Anyone have any ideas? Will try to take a picture.......
Truck is a 1997 F150, 2wd, 4.6

 

First guess, it's the vent hose for the differential.

 

Looked at a friends 97 F150. The hose connects to the brake line junction. Is this part of the ABS? The nipple that the hose would connect to is non exisitant.

 

My guess is the same as Ron's. My Explorer has a similar hose in the similar location that has a little clip on the end to attach somewhere. The clip somehow broke and it was just dangling there and my mechanic seems to have tied it off up underneath somewhere.

 

differential vent hose