Complex sentence: Simplified, this is a centrifugal force that throws the oil outwards against the coupling's housing, whose shape forces the flow in the direction of the "turbine" or "driven torus" (the latter also a General Motors term).
Split into simpler sentences: Simplified, this is a centrifugal force that throws the oil outwards. The moving fluid reaches the casing and the enclosed shape forces the flow in the direction of the driven impeller, referred to as the "turbine" or "driven torus" (the latter also a General Motors term).