1999 Chevy 1/2 ton Silverado 4by4

1999 Chevy Z71

What is the purpose of vacuum line attached to the rear end?


Differential Vent Tube

The vacuum line is a vent tube. This keeps the unit from building pressure internally. It also moves the point of entry above any perceived area of water exposure. For example, Suppose you were to back a boat into the water. The vent tube is positioned high enough not to allow water to enter into the differential that may now be under water.

differential vent tube diagram