Piston apparatus for use with vehicle clutches are disclosed. A disclosed drive unit assembly for a vehicle includes a housing defining a first cavity and a second cavity fluidly coupled together. The drive unit assembly also includes a clutch positioned in the first cavity. Rotation of the clutch conveys a fluid from the first cavity to the second cavity. The drive unit assembly also includes a port extending from the second cavity to the first cavity to receive the fluid. The drive unit assembly also includes a piston positioned in the first cavity proximate to the port and configured to operate the clutch. Movement of the piston relative to the port controls a flow of the fluid through the port from the second cavity to the first cavity.