Hello The ATF+4 in the gearbox has 6000 miles replacement interval and should be level checked 1200 miles. It must be replaced more often if you often run with heavy loads in the car. Make sure to use mopar ATF+4 when changing to meet the specs. I think i got an update on the last dealer service of the gearbox but it did not change anything that i felt. The ATF is replaced by dropping the container and replace the fluid. Unfortunetly there is no drain. Spill as little as you can and messure the ATF in the container. Change the filter, and clean the container using break cleaner and a clean cloth. Make sure to take out the magnet and clean it and check for wear. If you want to avoid leakage, use silicon selant and not the seal gasket. As the gearbox gets hot the seal tends to shrink with a probable leakage. Refit the container and torque in 3-4 laps up to 14nm. Wait for 1,5 hrs until the selant dries and refill the ATF. Start with the withdrawn amount of ATF. If you are to remove the entire amount of ATF from the system and do a so called flush you need to demount the line from the primary pump and drain there until fresh ATF comes out (while refilling the same amount during the process). Do not run the gear box with low level of ATF. Refit the hose and fill the box to correct level using a dipstick. The level differs depending on the temperature of the gearbox. Specs for this can be found on the internet. If you are doing this for the first time make sure to keep everything clean as always when working with all hydralics and make sure to get the correct level on the fluid. Place the gear shift in every gear for 1 minute and recheck the level. This must be done several times to make sure. Please note that this is my way of doing it. A flush should be done using a filter station etc but this is one way that has worked for me.