Diff Breather Kits
Differentials and gearboxes contain oil, but also air. As these components warm and cool the expanding and condensing air must be able to breath. So all of these components have whats called a breather.
However when fording or driving in deep mud/water the breather can become fully submerged, as the diff cools from the water it draws in air, With the breather underwater, water/dirt can be sucked into the diff. Obviously this contaminates oil and bearings and drastically shortens the life of the diff.
Extended breather pipes solve this issue buy venting the breathing of the diff to a high point such as under a bonnet or inside a snorkel (if fitted)