Oil specs are as follows:
Gearbox:
Audi OE part No: G052911A SAE 75 W 90 (1 litre, synthetic Oil)
oil spec: 75W90 GL4+ (suitable for synchromesh transmissions and hypoid gears)
capacity: 3.2 litre (fill to -2 mm +/-1 mm)
torque plug to ~30 lb/ft
Rear differential:
Audi OE part No: G052145A1 (0.5 litre), G052145S2 (1.0 litre)
oil spec: 75W90 GL5 (suitable for hypoid gears)
capacity: 0.9 litre (fill to lip/overflow)
torque plug to ~33 lb/ft
Both oils must be fully synthetic.
Opie oils recommended Gulf Competition 75w-90 (Ester based fully synthetic) as an alternative oil to the OE Audi oils that is suitable for both the gearbox and diff so I purchased a 5 litre tub for £52 which was a very good deal http://www.opieoils.co.uk/p-60162-gulf- ... 5w-90.aspx
First of all get the car off the ground using these:
The car must be level for draining to make sure you get as much oil out as possible and for filling to make sure the correct amount is added. I raised the rear of the car first using the diff casing as the central jack point, then the front using the point on the sub-frame where the gearbox mount attaches (see pic 4).
Tools required, including 10mm hex bit for all 4 plugs, torque wrench, extension bar and a hand pump with container (old 1 litre carton used here, cleaned-out):
Front jack point circled, gearbox drain plug (green arrow) & fill plug (red arrow)
It's always good practice when draining/filling diffs etc to loosen the fill plug first as you don't want to drain the oil to find that the fill plug is ceased. This is where the extension bar is needed.
Another pic showing the extension bar and ratchet used to remove the fill plug:
Then remove drain plug and drain oil, I used an old 5 litre screenwash carton with the top cut away, works better than a shallow drain pan as it catches more of the splashes:
I drained 3 litres from the gearbox, the oil looks fairly dirty dark brown so is well worth changing even though my RS4 has only done 38k miles.
After re-fitting the drain plug (there are no copper washers to replace) hook the hose from the fill pump into the fill hole
I removed the front left wheel to get better access to the pump as you will get a dead arm after pumping just 1/2 litre whilst lay under the car...I promise you!
From the front left wheel arch you will also be able to see the fill hole so you can keep an eye on the level, this is to be filled to just below the fill hole so keep checking with your finger.
Tools for the diff (+torque wrench), note only mid length extension bar is required for the fill plug.
Drain plug (green arrow), fill plug (red arrow)
I drained about 0.8 litre from the diff
and again looked a pretty dirty dark brown
Then fill in the same manner as the gearbox but this time fill until oil starts to overflow from the fill hole (no more than 0.9 litres or similar to what you drained out as over filling diffs can cause the oil to blow past the diff seals).
I spent a couple of hours doing this but I was taking photos and going at a fairly leisurely pace. It’s quite a satisfying job and would say the gear changes feel smoother, but my gearbox was pretty smooth anyway so those with stiffer gearboxes may find more of an improvement.
