Gearbox oil change is a specialist job, unless you want to pull the box, you need a specialist tool to remove the oil from the torque converter, possibly to fill it as well.
The ZF box takes specialist oil (9L) and it's about £30/L, there is no aftermarket option.
Couple of points aren't strictly true.
You can change some of the oil yourself very easily, wont be a full flush of the torque convertor, but approx 5 litres in the sump.
The gearbox is a ZF 6 speed auto and there are plenty of fluids that meet ZF specs that aren't Audi branded. Derivatives of the 6 speed auto are used in BMW's and Landover's.
I paid £15 a litre ish from Bristol Transmissions.
I bought genuine filter and gasket from Audi.
Regarding the special tool (VAG 1924) this is a load of rubbish, I don't know how they have convinced people a specialist tool is required.
I used a Hozelock pressure sprayer (7 litre capacity) to fill the gearbox, the 10mm flexible hose easily gets past the odd filler neck. Its then just a case of filling it till is glugs out of the hole.
There's a bit of messing around under the car, and you need VCDS to check oil temp as you shift through gears and check oil level again, but its all really straight forward and none of it is difficult.
I have a 2007 3.0 all-road and had to also remove a chassis brace to get the sump off, not sure if this is the same on all A6's.
It took me 2 hours and I went really slow and careful, it would take me 1hr now that I have done it.
As I say not a full flush but its so easy I would happily do again. I figure doing once every 50,000 miles is as good as a full flush every 100,000.
I did this about 1 year ago and have since put 20,00 miles on car. It drives faultlessly still.
