here is some interesting info I found below.
Avoid Incomplete ATX fluid changes
Changing the oil on an ATX involves dropping the ATX oil pan and replacing the mesh filter. Unfortunately this only changes 3.8L of oil with 5L of dirty oil and abrasive particles still remaining in the torque-convertor & gearbox.
To change all 8.8L of oil requires the following procedure: two large 20L buckets, one with 10L of oil, the other empty; hoses to the ATX oil cooler are removed and extended into the empty bucket; the engine is started for 1 second and the hose ejecting oil is left in the empty bucket whilst the now identified oil-intake hose is moved to the bucket containing fresh oil; the engine is restarted and run until only clean oil exits. Two people are required and Dealers do not perform such a service as routine - it must requested. Complete oil changes will greatly extend the life of the ATX.