Seems factory is Fuchs Synthetic, and lots of people like Motul 300 or Liqui Moly.
And lots of people ask about Mobil 1.
Of course all the discussions then break down into arguing over GL4 vs. GL5 in transmissions and the effect on brass syncros, and the question as to which fluids are ok/best for the Diff and center Diff are lost.
So is it ATF (or the proper kind), or Gear Oil (of the proper kind)?
Assuming your car is a slushbox:
Front diff takes gear oil. Automatic section takes ATF. Center diff takes gear oil. Rear diff takes gear oil.
Front, auto, center sections are combined into one unit with three distinct chambers. If you have ATF in your center diff, either someone installed the wrong fluid or you have an internal seal failure.
Growing old is mandatory; growing up is optional.
2005 A6 Sedan Q 3.2 (wife's whip)
2003 S8 (Q Ship)
2000 A4 Avant Q 2.8 (daily driver)
1999 BMW M Coupe (clownshoe)
1980 VW Scirocco (mid-life crisis car)
1983 Mazda RX-7 (revolutionary sports car)
1999 Mazda Miata SSB (track beotch, no plate)
2003 GMC Yukon Denali XL (the anti-earth)
2004 Dodge Dakota (hey, at least it's stick and 4x4)
Front diff is a plug with an 8mm allen socket right below the passenger drive axle flange. The torsen fill plug is also an 8mm allen on the passenger side of the torsen. Audi just calls for Synthetic 80w90 gear oil. Its the same torsen thats been used since the 80's. Its nothing special. Just use the mobile, my A6's has been full of mobile 1 for 20k+ miles now.
2000 Audi A8L 4.2
1999 Audi A6 Avant 2.8
1998 Audi A4 quattro 1.8T
Rear diff was fairly easy. Filler bolt was very tight, but once opened I found the Diff low.
Given the wetness around the axle seals, it was expected.
Took about 3 or 4 Oz of oil, maybe a little more. (Guessing a bit)
Center diff was next. It beat me. Diff=1 : Me=0
Between the limited space under the car (Front on ramps and back on jack stands), the angle of the plug, the exhaust in the way, I could not get enough leverage to open it.
Will come back to it next time it is on a lift.
Since the rear seal is wet and was showing bit of a drip, I really want to double check the level and top it up.
Front diff was easy. Off the ramps and stands, just jacked up the Rt front, took off the wheel and the plug is an easy reach with some extensions and a flex-joint. Plug came out easy. Made the dipstick (Bent wire) and checked the level. All was good.
Since the plug opened fairly easy, I guess it had been topped up sometime.
Did find that whatever "Mechanic" (and I use the term with a good amount of sarcasm) last worked on that corner should be flipping burgers (assuming he can do that without F-ing up).
FIrst the lug bolts were REALLY tight. OK, some tighten with time, but these one cracked come out so easy. A quick look showed that they had been coated with white grease (guessing lithium grease or maybe some spray Teflon grease), so they were obviously over tightened since the torque spec is for dry threads.
Next, I find the inner wheel well cover was rubbing the tire. Seems it was removed (or at least the front edge was unscrewed and none of the screws were reinstalled.
SO, I figure I will temporarily steal a few from the rear of the cover and at least hold the front in place and away from the wheel. Of course that did not work because the plastic clips the screws go into are all broken or missing. My guess is the "mechanic" either pull them out or over tightened them and broke the clips.
So temporarily the cover is held in place with plastic push in body pins.
I think I was trying the wrong bolt or plug on the center diff, so before the car goes to Buffalo for the winter, I am going to try one more time to top up the center diff.
So here is the question:
Does anyone have a picture or drawing of the transmission/center diff showing the filler plug?
I have looked on line and all I find are pictures from the drivers side, or cutaways.
If you have a spare transmission sitting, I would love a quick pic.