Optimized outer clutch housing for reduced spin loss, improved oil flow and improved clutch durability

A torque transfer device comprising:

• a housing assembly having a first housing member and a second housing member that are coupled together and cooperate to define a central cavity, the first housing member defining an annular piston bore, the second housing member having an end wall and defining a shaft bore, the shaft bore extending through the end wall, the central cavity being bounded on one axial side by the end wall;
• and
• a friction clutch having an input member, an output member, a plurality of first clutch plates, and a plurality of second clutch plates, the input and output members being received in the central cavity and rotatable about a rotational axis, the first clutch plates being received over and non-rotatably coupled to the input member, the second clutch plates being received in and non-rotatably coupled to the output member, the second clutch plates being interleaved with the first clutch plates;
• wherein a portion of the central cavity forms a lubricant sump that is configured to hold a predetermined quantity of lubricant through which at least a portion of the clutch rotates when the torque transfer device is transmitting rotary power;
• wherein a groove is formed into the end wall of the second housing member at a periphery of the central cavity, wherein the groove does not intersect the sump when the housing assembly is positioned in a predetermined position about the rotational axis, and wherein a portion of the output member and a portion of the groove are disposed axially in-line with one another.