Trans Cooler Line question

[mjm0103]

I don't profess to be much of a mechanic, but intend to learn as I go. So I apologize if the question sounds stupid.

I have a 69 Chevy C10, 350 w/ air. From the radiator are copper lines which I assume are for cooling the transmission. One of the lines (solid copper) leaves the radiator and ends up connected underneath the engine to a round unit (about 4" in diameter). The other copper line comes off the radiator where it connects into a rubber hose, then the rubber hose connects into the same round unit the solid copper connected into.

The rubber hose is old and leaking, so I'm going to replace it which is what caused me to have all these questions.

If these are the trans. cooling lines, shouldn't they head directly back to the transmission area? There are copper lines coming "out" of this unit that head back to the transmission.

Is the round unit a "pump" of some sort? If not, what is it? I've been scouring the internet looking for a schematic diagram or photograph of this area with no luck in hopes of determining what this unit is.

I have the Haynes manual, but it was no help.

Thanks
mjm0103