aTOMic

Found this to be perplexing. Or surprising at least.

Audi > A8/A8L > 2004-2008
6-Spd. Automatic Transmission 09E All Wheel Drive
39 - Description and Operation
.
Separate and Combined Fluid Systems

• Transmission with combined oil system:

• The oil spaces in front final drive and transfer case are combined together via return line - 2 - , supply line - 4 - and protective pipe - 5 - .

• The side shaft runs in ATF fluid in protective pipe.

• An additional transmission oil cooler - 1 - for transfer case - 3 - and front final drive - 6 - is attached to the transmission.

• Transmission with separated oil system:

• These do not have return and supply lines and transmission oil cooler

• The protective pipe is free of oil, the transfer case and the front final drive as sealed with a shaft seal to side shaft.

The .pdf has (only) that text, but shows an illustration.

I found another page which indicates checking ATF level is done at a plug next to where the transaxle attaches to the axle shafts (!) (pdf below).

Also attached is the "standard" procedure". Did those who've done their transmission (fluid change) remove the crossmember and use a jack to support the trans?
Also what plug / gasket materials are used; curious since they advise replacement.
-Tom

Mister Bally

I'm from the school of thought that if I see no leaks I leave well enough alone and don't look for ATF troubles. My '04 has 227,000 miles and I've done nothing with the transmission. Still running fine.

aTOMic

That really is amazing considering the weight of these cars, and the speeds some people drive and then post on youTube!
It's also comforting - since mine has 190k and hasn't been done to my knowledge. I hope you get a million miles out of it, Mister B!
-Tom

mishar

Everything in those PDF's is right. Checking oil level in the mid differential could be done without removing the cross member. There is a hole in it for that purpose. It is just not aligned well so it is serious trouble to tread the plug back in. On separate oil transmissions is not possible to drain mid differential oil (art of engineering ).

ATF level is checked at the big plug. Seal is metal (copper or aluminum?) and it is not absolutely necessary to change it if it is not damaged.

I couldn't find what perplexed you.

Panelhead

At 60K by previous owner, and I had it done at 72K because I do not always trust people selling items to me sight unseen. But the mechanic said the filter and fluid looked like new. With a car manufactured 10 years ago I expected at least discolorization if original.
At 200K I would not change either. If it shifts fine, leave it alone. Fresh fluid and a clean filter might cause issues.
I thought my garage stiffed me with 250.00 labor. But the more I see the procedure, the happier I am they did it. It is more work than I thought. And it will never get done again. At 150K this car is gone. Hopefully the electronics last that long.

mishar

Important rule for all A8 owners: You have to love her or she can be a real bitch.

She loves fresh ATF, oils ...

MP4.2+6.0

...at least on my W12.

For OP questions, little drain plug has a built in seal in a machined groove; not sold except as a complete plug w/ seal by either Audi or ZF. Pan gasket is (slightly) reinforced paper. ZF distributor sent me a metal one that looked nice, but the (BMW?) pan bolt pattern was wrong. Pan gasket is pricy from Audi; better to source from a ZF distributor (if they send you the right one...); the seals/plug then are less expensive too, as is the filter.

MP4.2+6.0

I have posted on that before. Search archives if interested. Mine has the combined system where the front and center (torsen) diffs share the same fluid. That also means the fluid becomes the pricier fluid with the special additive used in the Torsen now used in both diffs because of the shared fluid. ZF's materials (somewhat better than Audi/Bentley) say you don't need the special additive though if you are just doing a drain/refill; only spec'ed in new/rebuilt units with first time fills.

It isn't documented, but I think the combined systems are found in tandem with the gear oil cooler; in turn I suspect those are found only on the W12's and the S8's. Mine has both a diff oil cooler and a trans fluid cooler, mounted pretty much side by side underneath, just in front of the trans pan. I can drain the gear oil for both fronnt and mid diffs by dropping that cooler. As a result, BTDT.

MP4.2+6.0

the drain stuff is a given to me now on these units from what I have come upon. More on that below. But along the way it also may be part of getting at a specific component buried inside the tranny likely to cause issues for at least some of us longer run:

See picture below. 105K miles. It is the seal between the Mechatronics unit (a.k.a. valve body) and the guts of the tranny case/unit. Likely faulty one on top; new OE on bottom. Accessed by dropping the Mechatronics unit, which is right there in plain sight once the pan is dropped--it spans most of the pan size.

I searched high and low and found Audi related 6 speed tranny info slim to none. To be honest, I was disillusioned in the quality of some info in a tranny fluid post a few months back so figured I would just move on and let others tell their competing folklore while I pulled out the real tools and got into diagnostics and better research. I also think the board should move past the old "hoot" TSB that gets dredged up from time to time and get to more current info.; these cars have a lot more years and miles than when Audi, BMW and Jag issued their first versions of that TSB, for cars still under warranty and pretty young.

There is a lot more info about the tranny, and in turn the failures of this same seal, found for BMW's, commonly in their V8 models. Here is a link to one repair shop that spent the time to post a bit of info: http://www.autohausnc.com/zf-transmission/ The pictures of the same seal in their repair are even more sobering. And there are more to be found if you Google for images--as in, not a one off fluke most likely. Also to be clear, this is not an easy job--all the way up at a 9 or a 10 on the 10 point difficulty scale. The pan drop is already a pain, at least on the W12 and the S8 where the exhaust also has to come down and various other braces and shielding cleared away.

Along the way FWIW that bears on both ZF 6 speed tranny issues, I got this feedback from a ZF distributor and rebuilder I have used and trust over my last two higher powered Audi's :Read it carefully. My conclusion was, among other things, that cleaner fluid is that much more important. And again on some of the opinions or ideas floating around that I think are now arguably obsolete, notice the subtle reference to no more lead in tranny parts. This is an experienced manager at a name ZF rebuild distributor and shop with field experience inside these units which he is describing. That means concepts of letting the tranny just settle in from older historical experience have been upended by materials changes that no longer have the inherent lubricating properties they once did--just like a whole generation of old motor heads found with head rebuilds and valve seats when lead went out of gas in the 70's.

I can post more info., pictures and links in a separate meaty thread if there is genuine interest. In my case, I had a 6-5 shift down flare where it would drop to 4th and could kick to SAFE mode if I didn't back off fast. It developed pretty quickly, maybe over 5K miles from where I first heard a faint hoot type noise last winter on some higher gear kick downs at light throttle to the full blown 6-5 shift issues. I could sort of work around it with S mode or paddle shifting, but found myself reflexively starting to baby it/hesitate to make moves where the tranny needed to perform 100.000%. Needless to say, I don't plan to own a W12 and then drive it like a proverbial church lady. With full fluid and filter change per the complete 3x cycle in the TSB AND the code reflash AND full adaptation as my first go at it, disappointingly NO fix/change on mine. As in, with ALL steps of the "hoot" TSB done "by the book," no joy.

My exhaustive fluid drains never found more than dirty fluid--no metal bits, clutch stuff etc. whatsoever that are the bad news revelation sometime found w/ a pan pull alongside some tranny issue. That was my cue it was probably NOT in the conventional wear parts. I guessed solenoids and changed them in this same follow up job, but it could well be it was just the seal in the picture. The complete solenoid set was about $450 via ZF, so it didn't break the bank anyway. Other BMW posts suggest the seal can be tied to pretty harsh 1-2 or 2-1 shifts (clunks) and a variety of other things. They often do at least selective solenoid swap outs too. With a new set of solenoids and the seal change and a fresh adaptation, it shifts literally like new (I bought it back at 15K miles). I have enough miles on it now since I did the work to be definitive; night and day just as soon as the adaptation was done and the shifting settled in to its renewed form. Glad I got to the bottom of it with a definitive fix for mine.

Mister Bally

Wait until I post photos and a video from my recent run on the Bonneville salt flats.