A diff breather kit stops your differentials (as well as gearbox and transfer case) from sucking in water when driving through river crossings and large water hazards, leading to serious and expensive repairs.
As your vehicle’s differentials, gearbox, and transfer case heat up under normal operation, the air inside expands and increases pressure in the casings. To manage this increase in pressure, most of these components come standard with a series of one-way-valve breathers to allow the pressure build-up to escape.
However, when you enter a river crossing or large water hazard, the cold water quickly cools the expanded cases causing them to quickly retract in size; this forms a vacuum effect on the breather valves.
One-way breather valves will not let any air in, and as a result, water will often be sucked in through your surrounding oil seals allowing water ingress into your casings, axles, and differentials; leading to corrosion and serious damage.
To overcome these common issues, it is recommended to install a breather kit which acts similar to a snorkel for your differentials, gearbox, and transfer case. The breather kit is primarily a hub which transfers air in and out of the critical vehicle components; the kit includes a length of air tubing which is run to a high point (usually under the vehicle’s bonnet) where it is most protected from dust and water ingress when drawing air back in.
Out of the box, the 4 port ARB Diff Breather Kit can be connected to all four key components (front diff, rear diff, transfer case, and gearbox) and comes with enough tubing and fixtures to connect to the most common application of two differentials. With a small amount of additional tubing and fixtures (sold separately), the one kit will also accommodate your transfer case and gearbox.