This document tells you how to drain, fill and topup the oil level on a 4HP20 automatic transmission.
Note that you
MUST use Esso LT71141 oil in these transmissions.
The transmission holds 8 litres but typically less then 5 litres will come out when you drain the transmission, therefore you need to buy about 5 litres to do an oil change.
The oil level must be checked with the engine running and the car level, and you need to do this from underneath the car. I did this by putting the front wheels onto ramps, and axle stands under each rear suspension arm so that the car was level.
The document:-
http://www.aussiefrogs.com/forum/showthread.php?t=64323
