A heat exchanger assembly includes first and second heat exchangers integrated with a thermally actuated control valve assembly having first and second surfaces to which the first and heat exchangers are attached at various orientations to each other, including at 90 and 180 degrees to each other, and side-by-side. The valve assembly has two fluid ports for connection to an external fluid source, and two fluid ports in fluid communication with inlet and outlet manifolds of each heat exchanger. The heat exchangers may be a transmission oil heater and a transmission oil cooler, and the valve assembly controls the flow of transmission oil to the heat exchangers depending on the oil temperature. One or both of the heat exchangers may be brazed or mechanically secured to the valve assembly. The housing of valve assembly may be segmented, with each heat exchanger being brazed to one of the segments.