lightly grease a slow cooker.
in a large bowl, blend the sweet potatoes, 1/3 cup butter, sugar and 2 tablespoons brown sugar. beat in the orange juice, eggs and milk.
transfer this mixture to the prepared slow cooker.
in a small bowl, combine pecans, 1/3 cup brown sugar, flour and 2 tablespoons butter. spread the mixture over the sweet potatoes.
cover the slow cooker and cook on high for 3 to 4 hours. 