[Rich in Vancouver]

Having the gearbox at the correct temp and the car level when checking the level is critical.
The Freelander guys obsess over this and doing it properly does make a difference.
Even partial fluid changes of 3-4 litres (by just removing the drain plug and replacing the amount of fluid that comes out) help the performance of the box although Beinet1's method will get the fluid out of the torque convertor as well.