That's easy, only because the car is on the lift, engine & tranny are out sitting on separate stands. Front Diff is 8mm fill Hex/Allen (no drain plug so it has to be evacuated, fill is on the right side at the 3 o'clock position on the axle flange), center Diff is 8mm fill, 6mm drain (Audi, what were they thinking?), Rear Diff is 10mm drain & fill.