I'm reviving this thread, because the free end of the rear axle vent hose on my 2011 Ranger (std cab 2WD 2.3L auto) has come loose.
However, I do not see the sort of clip on the frame that others above have mentioned. Instead it appears that the rear axle vent hose might have been attached to a flanged hollow plastic plug, which is inserted in one of the small holes at the bottom of the bed support.
I have done a fair bit of googling, but most of the photos online show the end of the hose attached to the axle, rather than the other end. (At least I learned what the thing is and what it's for. That's a start!)
I gather from what I've been reading, though, that I could just MacGyver something to keep that vent hose up there, as long the hose stays a bit slack and I don't pinch it.