Items marked by the "gearbox breather" tag:

The design of modern cars includes a large number of components and assemblies, which are filled with technical fluids and lubricants. During operation, these fluids heat up, in other words they increase in volume, thereby increasing the pressure inside the car components and internals. This pressure difference must be leveled out to prevent depressurization, fluid leaks, and damages of car elements. For this purpose, some car components are equipped with a special valve, known as the breather.