ARB DIFF BREATHER KITA differential axle breather serves the important purpose on a 4WD vehicle of venting the air pressure in drivetrain assemblies such as the differentials, transmission and transfer case. Under normal operations, these assemblies heat up and the air inside expands, increasing the pressure and thus the need to be vented to the atmosphere is created. When the drivetrain assembly cools down the air inside contracts and creates a vacuum. Many drivetrain