auto gearbox oil change short cut?

read various threads, and as i understand it. the oil capacity for a td5 is about 10 litres. but only 5 litres can be drained out in one go. apparently the other 5 litres is still in the tc, cooler etc.
is there any reason why i could not start the engine and run through the gears for a couple of seconds or so, in order to pump more of the oil out?
feel free to ignore if a stupid question

yes you will be running pump dry ,oil from sump is sucked directly to pump, 5 litre change should be enough, oil is very detegent ,and normally fairly clean unlike manual gear box ,so oil will last longer than manual as your not needing to take contaminennts out so frequently,and any oil left in is at least filtered ,

thanks jamesmartin for saving my gearbox.

Some Land Rover service departments use a machine to replace the full amount although they still have to remove the sump replace the filter, my local indy has the machine. A lot of new cars with an auto box don't have a replaceable filter like my Honda

And that's the reason why ZF calls an ATF change an "oil purification" and not an oil change.

If for whatever reason you want to totally renew your ATF, need to carry out 3-4 "oil purifications" in a row, then at last change the filter.