It's worth pointing out that mine hadn't failed, I only replaced the radiator as a precaution after reading about the possible problem. You can see the rust beginning on mine and I believe it's the spread of rust that causes the joint to fail, that perhaps coupled with the slow failure of the o rings (as used to happen with the early LS400 power steering pump)
Here are some more photos that I think show the real possibility of impending doom!
The first is the radiator upside down showing the two connections that join the transmission via the rubber hoses, easy to access from underneath if raised up, the second is the bottom of the radiator cut away showing the cooler, the third shows just the cooler separated and how things were deteriorating. As you can see, the cooler is actually very small but in perfect condition in itself. And yes, the coolant needs to be drained but you don't really loose trans fluid, just a tiny amount.