I had a Trans Am once and it had a radiator with a built in tranny cooler. I figured this was pretty common on GM cars but did Subaru ever make a radiator like this. It would be a USEFUL spacesaver. A aftermarket one could be added, but thats taking away from its Soobness. I have never owned a A/T before, so maybe they already have one. Dunno...... Thinking of switching to a 4 speed auto.

How well do the built in ones help compared to an aftermarket one? I'm sure not as much but do they help at all?

There shoud be a small inlet and outlet on the bottom of the radiator - that's the tranny cooler. Most stock ones don't do much, but anything is better than nothing. An aftermarket one will be much, much better.

I believe the tranny cooler inlet / outlet lines are on the side of the Subaru radiator, not the bottem. Adding an auxillary cooler is quite easy and not too expensive. I just installed one on our Toyota Dolphin motorhome; total cost less than $60 and about one hour of work.