Simon,
Have you up graded your trans cooler mate, or is it stock!!! Getting a trans cooler from a 6.0L would be a fair amount of work I reckon, not really having easy access to any spares in australia hey. Maybe an after market one will be the go possibly. I need to do something. The gearbox has never been flash in it. Sometimes it takes up to 2 sec to change gears and other times it tries to break your neck, by snaping into gear. I will put it on the to do list which is growing by the day at present.