Unidentified part

When I was replacing the front drive shaft on my 2003 I noticed this pair of tubes that had rusted and become disconnected. They appear to have sintered filters at the ends of each. The assembly was only still there because its shape would not let it fall out. It pulled right and was not othe rwise connected to anything anymore. Can anyone tell me what it is and whether it is important? the truck is running fine with no warning lights on.

 

They're the breathers for the front differential and the ADD system. You don't want water in either of those, time for some new pipes.

 

Welcome To Tw...

 

Those are not filters on the end. They are check valves that allow air to escape as the fluid warms up in the differential.
They are placed high up on the inner fender to help keep from water getting into them.
The other ends that are rusted off connect somewhere on your differential.