ATF Temperature Test

[H2814D]

Hi all. Just some background info before I explain what I have done. I recently purchased a 2016 S5 Quattro with a Sport Differential. It had 900 miles when I started looking at it. Apparently, and prior to me finding it, this vehicle had been in a flood event at the dealership and was eventually sold at auction with 44 miles.

Prior to purchasing, I had my local dealer do a pre-purchase inspection. It came out ok, however, the mechanic reported possible fluid (ATF and Gear Oil) contamination, because of breather holes on the transmission body. I thought, if all that was wrong with it was fluid contamination, I could probably do the replacement myself. A local shop quoted $895 for the job.

So I began looking into the processes of draining and replacing the rear drive (differential) gear oil, the transmission and front drive gear oil (they use the same oil), and the ATF. All seemed relatively basic with drain plugs and filler holes. All I had to do was ensure I was using the right replacement fluids and quantities.

Easy enough, right? Actually, no. Internet searches turned up a lot of information, however, it could not be trusted. I finally contacted the dealer for part numbers for the various items needed. I ordered the downloadable Service Manual from FactoryManuals dot com. ($89)

The gear oil (trans and diff) drain and replacement went fairly easily. But the transmission fluid drain and relacement procedure turned up an interesting requirement during the procedure. It said that in order to properly do this job I would need to use a VAGCOM (or whatever it was) and check the ATF temperature during the process. The reported issue was fluid expansion at higher temperatures. The noted check temp was listed as 40 degrees C, or 104 degrees F.

So I decided to do a little experiment. I took three bottles of the replacement ATF. I made sure they all had the exact same starting liquid volume at room temperature. They did. I then put one in a freezer, at -- minus 17.7C/0F; kept one at room temperature-- 25.5C/78F; and placed one outside until it warmed up to 40C/104F. I then waited until all three bottles reached their expected temperature. Once they did, I opened all of the bottles to allow the air inside the bottles to be at the same ambient pressure, since warming and cooling of the closed bottles may have affected the bottle structure.

I then placed them next to each other. Guess what? All three bottles still had the exact same fluid volume as they did when I started. There was no difference, or if there was, it was not visible to the naked eye. So my question is, is that expensive VAGCOM and temperature check really necessary, or is it one more AUDI make-more-money-for them, and keep the DIYers at bay thing, that I seem to be finding out is relatively prevalent with this car maker? Unless my test was flawed, the actual ATF temp doesn't really make any difference. It doesn't expand as it heats up and it doesn't contract at lower temps.

Now don't get me wrong. I like the car and am having fun with it, and by the way I used an infrared thermometer to check the temp, just so I followed the procedure for warranty purposes, but is Audi preventing DIYers from doing something they could do on their own? I think so. By the way, after all of my work, I haven't noticed any drivability or transmission issues.

Try the experiment and see what happens.

[shonseb]

Actually you would probably find owning a vagcom very useful for DIY. Tons of user own one, including myself. You don't 'need' to own one, I'm sure you can find someone who owns one and would scan and make changes for you for a small fee. Many people will say also to use a carista app and dongle as an alternative to Vagcom, but I don't have any experience with that so I can't say it would do everything that Vagcom would. I would say that since the car was involved in a flood, that would be even more of a reason to own one in case issues show up later on. Then a scan can bring up codes that you can research to see what might be the cause of the code.

[doc280]

I can not say for the Audi 7-speed DSG, but for the Volkswagen 6-speed DSG, Volkswagen gives the same temp reading requirement. Statement coming from a Volkswagen master tech, the the temperature requirement is not necessary and most dealers will not do it because of time constraints. He said he has seen the VW DSG fill this way for years and never has saw a problem resulting from it. Also remember the dealer has a fancy machine to fill the DSG and the DIY way on the VW is to gravity feed it.

As for Carista, it works great and the interface is check blocks, so easy to use. I love it. Their customer service is great to, have a question e-mail them and a very detailed answer will end up in your inbox.

[JamesRS5]

The "check" temperature may just be exactly that, check the level is correct at 40'C and that will ensure the level will remain correct throughout the operating temperature range of the transmission.
It also may mean the transmission shouldn't have cold oil or relying on the just service level as the final level, ideally you'd service it, run it and check the level again to give the final service level. The 40"C may just be a good temperature to say the oil is circulated throuough the transmission and the correct amount is in the sump.

The transmission operates at a much higher temperature then 40'C after all.

[snocat17]

Few things: Oil volume at low temps (0F) probably doesn't change much from 78F, so I wouldn't expect to see much there. And going from 78F to 104F is also not a big jump in terms of volume expansion. All three temps would be considered "cool" in my opinion.

I would think your normal operating temp for your tranny would be north of 150F, closer to 180F depending on your driving style. That is where volume would be critical. I am not sure why the ATF volume at 104F is so important for Audi, but apparently it is.