7.3 Transmission Cooler Line Diagram. Below is a basic silverado and sierra transmission cooler line diagram showing the standard hot (send) and cool (return) lines as the flow through a factory cooler setup. Install the transmission lines according to the figure 1.
As the gif above shows, the bottom line is the hot line which sends warm transmission fluid out to the factory trans cooler within the radiator at the lower port in most cases. The truck is a 2000 f350 with 7.3 and 4r100. The bypassing of the cooler was supposed to happen until the fluid reached operating temps.