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

A5/S5/RS5
#29

Just to be safe, I’d change them.

Audi’s recommendations are based on mileage as well as time for most items. Their main service intervals list time as well as mileage but they don’t necessarily specify that for each individual fluid. Fluids can degrade over time due to condensation/water contamination and outgassing. Just how bad do any of the transmission fluids get over a period of sitting stagnant for years? Dunno honestly, you’d have to send them out for testing. But it’s relatively inexpensive insurance to swap them out vs. developing an issue to fluids which are out of specification. Plus you’ll know they’ve been done and hopefully done correctly.

Short version, you can’t hurt anything by swapping the fluids out. The MTF side of the transmission is sealed, the ATF side does have a vent. On the rear diff, it’s sealed as well but you’re already at 17K miles on those fluids plus time.

The rear differential is fairly easy to change. I’d say, at the very least, change that but the other stuff can wait until fall. If your car is shifting erratically or what you deem to be “not normal” then I’d consider changing the fluid sooner than later. If you’re planning on doing track days, I’d definitely change the fluid all around.

#30

Fantastic, thank you for your feedback.

The transmission is shifting fine & I have no plans for any track days, so there’s no particular urgency to change the fluids on that front. However, I’ll still make a point of borrowing a friend’s garage for a day & changing all the fluids, based on your recommendation. And thanks to your detailed instructions, I have a list of all the tools & materials that I will need to do the job! As you can imagine, part of the hesitation to do this kind of work in someone else’s garage is not having all your own tools there so I’m really grateful for all the work you put into making these instructions & putting them online.

Take it easy!

#31

Most welcome and sorry for such a late reply! I’d typed all that out a while ago and then forgot to hit the “reply” button! The forum saves your posts so when I logged back in, I saw I hadn’t actually responded. So my apologies.

#32

It’s all good. I didn’t get the stuff from ECS until yesterday anyway. Plus I’m hardly in a position to complain about getting experienced advice for free. Furthermore, a fellow Audi/VW enthusiast friend has offered me his help & garage for July 10th so I wasn’t in a position to do it earlier than that. It turns out he actually wants to go through the process with me on the RS5 & then get my help to do the Haldex service on his Golf R if we have time that afternoon. After that we might undertake the same DSG & differential service on his C8 Allroad at some point. So it all seems to be coming together very well!

Otherwise once I’m caught up on the overdue maintenance items (which are only overdue in terms of time rather than mileage), I will get back in touch with you regarding other upgrades. I have no plans to take the car to the track, but I’m intrigued by the JHM tune (although a little intimidated at the thought of installing it). Plus I’ll be getting a set of the standard JHM rotors at some point, which I suspect will be just fine for street use assuming they are similar or better than the OEM wave rotors. Since the car has been parked for 4-5 months every winter my wave rotors are getting a little pitted. One way or another I would like to contribute to your efforts!

#33

On the JHM tune (installation), don’t be afraid of that. Assuming you saw my video on the tune installation process? I actually make myself available before, during and after the flash if necessary and I walk you through the entire procedure. Just shoot me an email, sales@redmistracing.com for best pricing. It’ll completely transform the car. Really does wonders. Pair it with the RMR transmission cooler and heat soak is pretty much eliminated and reliability is improved.

It’ll be a LOT to do the transmission/diff service and th en his Golf R in one day. Does he have a lift? That’ll make it easier. I really, really like the measure methodology, measuring the old fluid, adding a tiny bit for spillage, and using same amount to re-fill. If you use common sense, it makes it very easy to get the refill level right without the tedious process of checking it per the factory method. It’s worked for me time and time again.

JHM’s rotors are the best value out there, are more than capable of doing track days and are far better than OEM rotors. Since they’re semi-floating, they can account for radial expansion and if/when the rotors wear out, just replace the outer rings and save $$$!

#34

Wow thank you for all the info. I will send you an email so we’re not making this thread unnecessarily long.

#35

Adding to this as my as my gearbox MTF ie gear oil change is coming due I really wonder if 3k km intervals under normal use and no tune is not unnecessarily short. The S5, S7 are running the DL501 with compressor and turbos respectively and have no MTF gear oil change same as for thr OBC rear diff. For drivers doing most kms on the highway might just be waste. Similar to why we should change air filter every 3k km. Any thoughts on this? everyone welcome

#36

The gearbox oil is changed every 20K miles (imperial). Not sure if that was a typo (3K Km would be far, far too short!) and you meant 32,000 Km?

I’m part of a Facebook DL501 message group which is almost entirely composed of S6’s having issues with their transmissions, albeit mostly with the mechatronic side but not always. Having spent some time in this group, I can say I will never own an S6 as the problems they 're having, and frequency, is truly staggering.

Then again, they don’t have the option of a turn-key bolt-on transmission cooler like the RS5, S4 and S5 guys do :slight_smile:

What you could do is capture some of the old oil next MTF change and send it out for analysis. That would give you a clearer picture.

Just remember, our cars turn another 2,000 rpm higher at redline than the S6 and I’m sure that has some effect.

#37

One explanation could be the crown center differential, if it really is true that it was only ever used on the B8(.5) RS5/4 and no other models. Some USP if that is true, although it was used to sell some other models around the same time.

#38

When loosening the MTF drain plug, is there a risk you damage the connector with the 26 mm socket if pushing upward too far or not using a longer socket?

#39

I would think the socket would just bottom out. I use a deep scoket but that is an expensive sensor if broken.

#40

Does the S5 have the same torque vectoring system (brake controlled as the RS5)?
Wondering if that and centre crown combined justify this or shorter intervals.

To that end, I am doing an oil sample test with the change, as suggested by @Ape_Factory , at 30’ kms. It costs about the same as that sensor but is done by German tribologists.

Would be interesting to compare against Motul 300, which costs a lot less here than OEM MTF, after 10.000 kms or so.

#41

MTF analysis results as mentioned above

Screenshot_20221104-192542_Chrome
Screenshot_20221104-192542_Chrome720×1600 276 KB
oil analysis company told me there was some more oxygen in it than they expected and silizium (from seals) was slightly higher than they recommend. Everything else was lower. Hard to say really but the raw data is there. Changing gears at most marginally smoother. Feels like I could have waited another 10-20k kms but I play safe. BTW I appreciate input a lot on this since I find funny only the RS4/5 B8.5 has such a short interval in audi or as I know of.

#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.