Oil/Transmission cooler lines.
There is a heat exchanger in the passenger side radiator tank for the trans, and another one in the driver side tank for engine oil.
The lines connect to an adapter above the oil filter for the engine oil cooler (your truck may or may not be equipped).
The other side, the lines connect to the trans. EVERY automatic-transmission vehicle is equipped with this.
To install an aux trans cooler, you intercept the line returning to the trans from the radiator tank.