Does my 04 xj8 have one?

No, there is no means of draining the torque converter, which means getting new fluid throughout the tranny needs more fluid than just replacing that in the pan. A flush is needed and thus some new fluid will get contaminated by the old stuff. Of course, one can always just replace the fluid in the pan and ignore the stuff in the TC. Thats what a lot of people do, and it is normally satisfactory.

I wonder if anyone has tried the DIY flush. Disconnect the cooler lines. Put the out in an empty bucket and the in into a container of ATF. I have done it on other cars. Worked fine as long as you don't let the in bucket run dry.

I guess not. It is easy to do and flushes out all the old fluid. You only waste a liter or two.

Don't even have to drop the pan although that is best.

Seems to me that this is the only way to do it ,i mean whats the point doing it via fill hole 3 litres in max ,esp if youve had a leek and unsure whats in there to start with??anyway im going try it .I MAY BE SOMETIME LOL.

If you look in the first Sticky above, go down the list to Transmission you will find years of experience recorded there.