A transmission sump screen for disposition in a transmission sump is disclosed. The transmission sump screen includes a mesh of viscosity sensitive orifices providing a predetermined permeability to selectively segregate the transmission sump into a first volume and a second volume depending upon a transmission fluid temperature. Transmission fluid is only drawn from the first volume until a threshold temperature is reached. The transmission sump screen includes a first portion having an outside edge abutting the transmission sump and an inner edge spaced from the outside edge to define a neck region of the first volume having a first periphery. The transmission sump screen includes a second portion extending downwardly from the inner edge of the first portion to a lower edge abutting the transmission sump to define a lower region of the first volume having a second periphery that is larger than the first periphery.