A switchable valve train assembly including a carrier housing defining a hydraulic circuit, a supply assembly, a plurality of rocker shafts, a plurality of separators, and a plurality of rocker arm assemblies is provided. Each one of the plurality of separators divides the rocker shafts into (1) a first chamber extending between a first chamber axial end and the separator, and (2) a second chamber extending between a second chamber axial end and the separator. The plurality of separators each include an orifice defined between the first chamber and the second chamber that provides fluid connection between the first chamber and the second chamber. Locking assemblies of the rocker arm assemblies are selectively actuated based on the supply assembly. The separators ensure that hydraulic fluid within the hydraulic fluid is de-aerated and that the second chambers remain primed with hydraulic fluid for faster actuation of the locking assemblies.