Silver Vent tube?

I know this is probably a dumb question but I am completely stumped and with it being so cold here in Wyoming I haven't wanted to lay under the Cherokee for a while. I have a 2000 Cherokee with the 4.0 Litre and looked underneath and a rubber hose with a plastic fitting on the end covered with a silver heat shield was hanging down. It looks like it might be a vent tube....does anyone have any suggestions?
Thanks in advance!

Where underneath; front, middle, back, left, right or center?

It is located in the center and is hanging down by the diff. It looks like a vent tubt that is attached to the firewall at the top with a vent.

front diff vent?

That's what I was possibly thinking....where does the vent attach? At the top of the diff?