98 explorer eddie bauer, noticed this morning a loose cable dangling from under the rear of my truck, close to the rear differential and touching the street. on closer inspection looks like tubing, nothing draining from it. photos attached. would appreciate help in identifying and how soon i need to visit the shop. thanks

 

It's the axle tube vent.

It's supposed to extend up to the frame (note the clip) and then hang or extend 'downward'. That way, the axle can vent, and water spray under the vehicle can't run 'uphill' to get into the axle vent tube from the hose end hanging downward. Some vent tubes will have a plastic cap on the end that allows for venting, yet keep debris and water from entering. As long as a portion of the hose hangs downward from the frame attaching point, water generally won't climb up a hose..