help--- RADIATOR/TRANSMISSION FITTINGS (BRASS)

They can be called several names. The "proper" name for the flare is "SAE." This sets it apart from JIC /AN, which is a 37 degree flare angle and in some sizes, different size thread. SAE (normally brass, not always) is 45 degree flare. This is most common on older US cars, and hardware such as ice machines, and all older refrigeration equipment, IE coolers, freezers, older AC units

JIC / AN is often used on hydraulic stuff like industrial and farm tractors.

What you want is

.... sometimes called a "half union" that is a "union" would be flare both ends. also just sometimes called an "adapter."

Pipe on one end, SAE flare on the other. I have never seen JIC /AN fittings in brass, only aluminum or other alloy, or steel

So you want a "half union" or adapter in SAE flare, and whatever pipe size by whatever flare size.

Most cooler fittings are 5/16 flare. That is, flare is called out by the tubing size.

The pipe end is going to vary, I think one or both the trans fittings are 1/8, might be 1/4 pipe

Pipe is called out by it's nominal ID

Smallest COMMON size is 1/8 pipe which is roughly 3/8" OD, then 1/4, then 3/8 which is roughly 5/8" OD (You can use a 3/8 pipe nipple to connect two 5/8 heater hoses, EG)

OD of pipe thread for identification

stpats.com/manuals/MEP%20manuals/corkerNewManuals/NPTSizing.pdf

This chart compares different types

SAE is towards the bottom, notice below that is inverted flare which is your brake stuff

"Tube size" is along the top in sixteenths of an inch, that is, 5 is 5/16 which is where you get the "number sizes" used in AN fittings

brennaninc.com/documents/BrennanThreadChart.pdf