Full S-Tronic and rear sport differential service (RS5)

A5/S5/RS5
#42

So that’s the OEM fluid which was tested? It’s strange on the intervals but I’m also part of a mostly S6 information group that’s dedicated to fixing the DL-501 transmission. They have a much higher failure rate on the S6 (both sides, mech and gears) than the RS5 from what I can tell. Then again a lot of S6 guys are adding a lot more hp/torque with their mods on what is ultimately a significantly heavier car.

I’m really of the opinion that the ATF side frequent changes are the key. There’s nothing special on the MTF side that would require more frequent changes than any other high performance gearbox. I can’t see the gear tolerances being tighter on just the RS5 and no other model. Can’t see the crown diff causing increased wear either. Gear shear is going to do most of the fluid breakdown.

The Motul has a VI of 220 or near there which is quite high. Even their 300V LS has a lower VI rating. But really the problematic side is the mechatronic. Sticking with, at a minimum OEM fluid change intervals and using the RMR transmission cooler kit works wonders.

#43

Their iron wear rate indicated (and others) I could have gone another 60k kms. Oxygen level in their comment maybe indicates is not completely sealed. If it wasn’t a hassle to get to I’d check the oil level and take a sample after 30k. This probably verifies a 30k interval is reasonable for hard use (if not more often) and ATF and oil should be changed more often. Heres a theory: the other cars dont have MTF interval changes, whereas ATF and engine oil intervals if was shorter for only the RS5 maybe questions would be asked. It is audi OEM gear oil, should send them a sample of the new oil or if I got the reading would tell us more. Maybe someone of the S6 guys have an ATF sample would be interesting to see.

#44

Si, which us Yanks call Silicone cam be from many sources and yours isn’t high enough for it to be a worry. can be seals/sealant, oil additives (anti-foaming), dirt/dust (Oxygen?).

#45

I was going to suggest it might not be a worry. It’s all playing safe. I’d bet everything except my car it is all good for another 30k kms at least

#46

About to do the gearbox ATF. Would you bother with a flush (ie with detergent): https://www.automatikoelwechselsystem.de/wp-content/uploads/2022/07/AGSG-05-2022-interactive.pdf

Or is that unnecessary/does more harm than good potentially since we have two filters in the model range. Ie would it suffice flushing with extra new oil (cheaper) then doing a final drain and filling up.

#47

You could use cheaper but still approved oil to push out more of the old stuff. On the ATF side, it’s necessary to drop the pan to change out the internal filter and clean the two big magnets on the bottom of the pan.

For adding more oil, there’s a vent on the top of the transmission. The cap pulls right off with ease. Can’t remember what size the nipple is off the top of my head but you could attach a hose to it with a clamp and pump fluid in that way to flush it.

#48

I take it we both tilt in the direction of using detergent when flushing the old oil (I imagine mainly for the wet clutch) probably makes less sense.

#49

I’d err on the side of caution and not use detergent. Unless Audi specifically has a formula they know won’t hurt the clutches. A normal automatic with a torque converter is a far different animal from wet multi-plate clutches.

#50

Agreed. What’s more, they are not using the A2 suffix ATF but equivalent to and not even VAG original , although I wouldn’t know the difference between A2 and standard.

#51

Just for the record, I think it makes sense if one is experiencing issues/symptoms with the transmission to do this service instead of regular.

#52

What view do you here have of Shell DCT M1 , if any. Allegedly the best ATF on the market.

Characteristics Standard Shell DCT-M1
Kinematic viscosity @40 C mm2
/s DIN 51 562-1 31
Kinematic viscosity @100 C mm2
/s DIN 51 562-1 6.8
Viscosity index DIN ISO 2909 187
Dynamic Viscosity @-40 C mPa s ASTM D2983 9.150
Density @150C kg/m3 DIN 51757 848
Flash point 0C DIN EN ISO 2592 202
Pour Point 0C DIN ISO 3016-51

#53

Much of the Shell numbers seem to be an Apples to Oranges comparison compared to most ATF specs, using different specifications. From what I do see it looks to be one of the thinnest DCT fluids but again, hard to compare without being an expert on the testing standards. It appears to be a fluid meant to meet the newer Mercedes spec. Most ATF’s nowadays are going to thinner oils, ie ZF Lifeguard 5, 6, 8, for example all get thinner over the years, same as the GM Dexron specs. All about low friction/drag. I don’t know think I would go to a DCT fluid much thinner than the average DCT viscosities.

#54

Thanks. I found another expert, who uses 10 litres Motul to flush and replace the old.

#55

This is why I run Liqui-Moly 8100 as it’s on the “thinner” end of all the Audi-spec fluids. I do this mostly for heat transfer reasons. Something like Amsoil’s fluid would be on the opposite end of the spectrum. We’re talking a fairly small difference though. It’s also a lower viscosity than the Shell. I don’t see a VI number for the Shell either.

Shell likely makes the base refined oil for many of the oil/transmission fluids on the market but it’s the additives packages which are different. It must have the correct friction modifiers and specific additives content to meet Audi’s specifications. Get it wrong and things can go bad, quickly. Just remember the whole PCB board issue with the DL501. That was partly caused by the transmission fluid itself which wasn’t “compatible” with the PCB’s casing. It eventually ate through the casing and shorted the PCB.

There are certain things I try not to second guess the engineers on, fluid compatibility being one of them.

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#56

I’d actually advise against doing a detergent service for a number of reasons. Find a photo of the valve body, opened up, and understand just how small some of the passages are. I think you’d be asking for trouble using a service procedure like that. Solenoids too…some very small orifices.

With that said, modern oils and their own detergent packages are very efficient at keeping components clean. Most of the residue found when servicing the mech is clutch material, not gummed up oil.

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#57

Considering Audi does not open it up to clean the magnets and change the internal filter. Otherwise, I’d let them do it, if at a half reasonable price. Such a rip-off for them to put in 6 out of the 7 liters only, ie not do a proper change. Next time I am in Germany, will happily ask them just to get it done, as I am not sure I trust the pumps in the self-service garages

#58

Definitely worth airing on the conservative side on changes as APE has preached in the past. I think of all of Audi’s services as a minimum. I just sold my 27k NSD gearbox to a repair facility on the other side of the country as they had a customer car (w/70k) with a failed gearbox (who knows what was really wrong with it) as they couldn’t get a replacement from Audi for 6mths~1yr, and they were told just under $10k for the gearbox. Maybe I should have retained if for a spare for myself?

#59

I believe Audi changed their stance on that back in 2012. Its standard operating procedure to drop pan, clean magnets and replace the filter, at least here in North America.

#60

Not here in Europe, unfortunately, per my dealer rip-off receipts and offers. I knew they didn’t change the internal filter or clean the magnets, but somehow thought they dropped the pan anyway and at least changed the all 7 liters.

I never double checked before, as I assumed they did the procedure you are explaining. I bought myself an electric engine oil drain pump that runs off the battery. I will do the change myself per your instruction video, at a self service shop, and try to use it. VAG original ATF is fairly inexpensive at 6 liters at under 100 USD.

#61

Wow that’s unfortunate on the no filter change policy. I mean if you drop the pan, it’d be stupid to not clean the magnets/change the filter. Takes 10 mins tops at that point.

I have to go look again, but pretty sure the VAG factory fluid here is like $30 a liter or more. The rear diff transfer case fluid (ATF side) is about $50/liter with tax! Thank god you only need one bottle…so six liters at under $100 is exceptional.