Raptor the axle has a vent because the fluid gets hot and cold (expands and contracts) so the vent is to relieve pressure. If the vent gets clogged with dirt or mud, then the next easiest place for the pressure to be relieved is seals, usually end of the axle tubes. Then you have a mess, and need to replace them

Cut off the old rubber from the bottom of the axle fitting, by slicing through the rubber top to bottom, and just peel it off, and just push the hose back on there. While you got it off, blow some compressed air through the vent tube and make sure its not clogged any.

If you really wanted to take it a step further for a more permanent fix, replace the 2' of rubber hose and reconnect it top and bottom with new rubber line.

 

Axle vent tube

 

patman hit it right on the head.. just a piece of simple flexible hose will do and then extend it up zip tie it and away you go