Hello All
The Very best Trans Cooler I have ever used is one made from an old Air Conditioning Condenser.
I used one of the Add On Air Conditioning Condensers like ARA, it was the type that had a Flat Tube bent back and fourth to make the condenser.
It will take a little adapting at the fitting ends to fit the trans cooler lines, but it works really great.
The proper way to install it or any other cooler is to install it so the fittings are at the top and bottom of the cooler, the HOT fluid comming in, connects to the bottom of the cooler and the return COOL fluid comes out of the TOP of the cooler. This allows the cooler to constantly blead out any TRAPPED AIR, this will make the cooler as efficent as it can ever be at removing the heat from the fluid.
Hope this helps
Dusty