No S Tronic is dual clutch, 7 speed used on 3.0TDI 218hp model. Tiptronic is single clutch with torque convertor and 8 speed.
Both need serviced. S Tronic every 38k miles. Tiptronic then Audi will say sealed for life. I don't buy that as there's a ZF8 maintenance kit specifically for it, so I did it earlier this year when it turned 60k miles.
Absolutely critical these boxes are maintained as auto gearbox replacement is ridiculously expensive.
On quattro, the rear diff gear oil should be changed too anywhere from 60-80k miles.