A transmission thermal control system, comprising a transmission cooler having an input and an output, a transmission sump and a bypass valve comprising: a manifold comprising: a first port configured as a first fluid input port; a second port coupled in fluid communication with the first port and configured as a first fluid output port; a third port in selectable fluid communication with the first port and the second port and configured as a second fluid output port; and a fourth port in selectable fluid communication with the third port and configured as a second fluid input port; a first conduit connecting the first port and the second port; a second conduit connecting the fourth port to at least an opening of a third conduit (118a, 118b), the third conduit extending from the first conduit to the second conduit; a valve stem supported for linear displacement between a first valve position and a second valve position; a first sealing element fixed linearly along a length of the valve stem; a second sealing element fixed linearly along the length of the valve stem, spaced apart from the first sealing element; wherein the third port is located between the first sealing element and the second sealing element, an axis of the third port is perpendicular to a plane formed by axes of the first conduit and the second conduit (108, 117), the first valve position disposes the first sealing element to close the third port from fluid communication with the first and second ports (104, 106) and disposes the second sealing element to open the third port to fluid communication with the fourth port, the second valve position disposes the first sealing element to open the third port to fluid communication with the first and second ports (104, 106) and disposes the second sealing element to close the third port from fluid communication with the fourth port, the second port is fluidly coupled to the input of the cooler, the fourth port is fluidly coupled to the output of the cooler, and the third port is fluidly coupled to an input of the transmission sump. a manifold comprising: a first port configured as a first fluid input port; a second port coupled in fluid communication with the first port and configured as a first fluid output port; a third port in selectable fluid communication with the first port and the second port and configured as a second fluid output port; and a fourth port in selectable fluid communication with the third port and configured as a second fluid input port; a first conduit connecting the first port and the second port; a second conduit connecting the fourth port to at least an opening of a third conduit (118a, 118b), the third conduit extending from the first conduit to the second conduit; a first port configured as a first fluid input port; a second port coupled in fluid communication with the first port and configured as a first fluid output port; a third port in selectable fluid communication with the first port and the second port and configured as a second fluid output port; and a fourth port in selectable fluid communication with the third port and configured as a second fluid input port; a first conduit connecting the first port and the second port; a second conduit connecting the fourth port to at least an opening of a third conduit (118a, 118b), the third conduit extending from the first conduit to the second conduit; a valve stem supported for linear displacement between a first valve position and a second valve position; a first sealing element fixed linearly along a length of the valve stem; a second sealing element fixed linearly along the length of the valve stem, spaced apart from the first sealing element; wherein the third port is located between the first sealing element and the second sealing element, an axis of the third port is perpendicular to a plane formed by axes of the first conduit and the second conduit (108, 117), the first valve position disposes the first sealing element to close the third port from fluid communication with the first and second ports (104, 106) and disposes the second sealing element to open the third port to fluid communication with the fourth port, the second valve position disposes the first sealing element to open the third port to fluid communication with the first and second ports (104, 106) and disposes the second sealing element to close the third port from fluid communication with the fourth port, the second port is fluidly coupled to the input of the cooler, the fourth port is fluidly coupled to the output of the cooler, and the third port is fluidly coupled to an input of the transmission sump.