Hi,

periodical ATF change is not requested in any Audi maintenance manual - unfortunately! To make an automatic gearbox has an optimum lifetime, it is most important, to change the ATF and it´s filter(s) or strainers assiduously and periodically. And you must never refill old ATF!

ATF strainer changes are not discribed in Audi manuals. Only ATF change, checking and adding the oil level are mentioned.
ATF is available at many distributors. Oil strainers are not available at Audi dealers and must be procured at special services (for example at specialists in gearbox overhaul). A new seal for the oil pan is needed as well.

I have been driving a several cars (of different brands) with automatic gearbox and I have changed oil and filters generally every 40000 kilometers. Only on my Citroen XM V6 automatic I have changed the ATF every 10000 kilometers (at every enigine oil change), because this gearbox is well known for a lifetime of less than 150000 kilometers. On my citroen, the gearbox has been working for nearly 400000 kilometers without making any trouble.

As the maintenance conditions of the at-gearbox are indefinite or known bad, I would proceed like this:

Change ATF and oil strainer. Drive for about 1000-3000 kilometers and change the ATF again. This is good for rinsening the system, because a few liters of ATF allways remain in the torque converter so, that you can never drain the complete oil content.

On the V8 the filling quantity is about 3 liters ATF (without strainer) after draining the ATF at the drain plug.
The difference on the dipstick between maximum an minimum is 0,6L

Beste Grüße
Tim