The S-Tronic (DSG) gearbox has a MTF (Manual Transmission Fluid) & ATF (Automatic Transmission Fluid) (BTW, so does a Sport Diff). For the S5 Audi only says to replace the ATF in the DSG but not the MTF. The RS5 has basically the same transmission and Audi says to do both? Most would say if you want to keep your car in great condition, do both. Haldex is only for the TT & 3 series cars (A3, S3, RS3) with transverse mounted engines. For the rear it depends on what you have. The sticker in the trunk/spare tire wheel well will have your options codes with your engine, transmission, and rear Diff codes, the sticker is also mounted on the inside front page of the Mx booklet that comes with the car too. Regular diff just has gear oil and like any regular diff just takes 75w/90 Synthetic GL5 gear oil. The Sport Diff as I mentioned above has a ATF side and MTF side. Once again the RS5 gets both sides changed and the S5 doesn't. Do both sides, it doesn't take a whole lot of fluid. Keep in mind a transmission and/or Diff are a fortune to replace so a little Mx is great. Audi's service intervals should only be considered Maximun intervals, most change these, including the engine oil, more often. Cheap insurance.

Great thread here: https://www.audizine.com/forum/showt...ht=DSG+Service