X2
I added an aftermarket Hayden trans cooler to my car, but as Roy suggested, I didn't maintain the stock trans cooling lines in the radiator. As a result, it does take awhile longer for the trans fluid to heat up on cooler mornings, but not using the internal radiator also meant less potential leaks from multiple line connections. The added engine cooling gained by eliminating the trans cooling lines from the radiator was just a bonus.