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I just completed the oil changes for the DCT and differential, according to the instructions in WIS. There have been a few very good threads on this topic with some creative ideas and I didn't want to do yet another one. But, in reviewing all of those I saw a potential to get the fluid levels very wrong. It might explain some of the comments in posts where the fluid quantities seemed off or not correct. Hopefully, those doing this DIY in the future can use this as an addendum to those threads.
If you have access to a chassis lift, then this is not an issue; however, if you're doing this DIY on a garage floor with floor jacks, then this is important for you. I did this job on my garage floor using two floor jacks and raising the rear end to a working height. I knew from past work on ZF transmissions, this is a problem but I thought I'd create a project so I could illustrate the error in hopes of helping others.
It is essential the chassis be level for the drain/fill operations of both fluids. WIS instructions specify a lift (step 4) and doesn't assume this job would be "backyard" performed on jack/jack stands. Yet, there are those of us out there doing it this way. When I find myself doing a job like this off a lift I establish TWO working heights
Comfortable height to remove parts, loosen drain/fill plugs, etc.
Lower height to get the chassis level especially for the correct fill levels.
I go back and forth between these two heights. The MISTAKE is doing this entire job (drain/refill) at one raised level where the chassis is on a gradient. I'll demonstrate this below:
I set the rear end up on floor jacks that gave plenty of room to reach everything. I used a magnetic level on the chassis. The gradient was 3.90* biased to the rear of the car (of course) and that took into account the pitch of my garage floor the other direction (as most garage floors are built today).
Here is a pic of that position. The level is difficult to read BC with a 3.9* pitch the level bubble disappears. But take note of the distance the rear wheels are off the floor.
I then proceeded to follow the steps in WIS to drain the differential part of the transaxle. Without rewriting those steps, it's pulling the drain plugs and the fill plug (which determines the correct fill level). It is only this half of the process I will demonstrate, but same issue applies to the DCT part of the oil change.
So, the fill step involves pumping new fluid into the fill hole until it drips out. HERE IS WHERE THE MISTAKE IS. With the fill completed and the chassis still at a 3.9* slope, I positioned clean bottle under the fill plug opening, then I lowered the car to LEVEL on the bubble level. Here is a pic of the car lowered to the expected 0* pitch and you can see the difference in the rear wheel height. The rear wheels actually touched the floor a little to correct for the floor pitch. In this position, the car is very low and too low to comfortably work all the functions, but necessary for the correct fill.
So, with this new position (a difference of 3.9*) additional new fluid spilled out. A total of 1/2L!
Bottom line, had I left the car in the higher jacked up position, I would have overfilled the differential by 1/2L. The same applies to the front DCT oil change (but likely more than a half liter).
Use two heights - One higher height to get the hard work done. Then a lower height (I use shallow drain pans and containers) to ensure the fills are correct.
I wanted to finish this addendum with a final input. When I did the oil change last week I kept the undercovers off. I did this so I could test drive the transaxle under some different higher speed circumstances. Then, I want to recheck the fluid levels in both the differential and the DCT. I did that now yesterday and verified (to myself) the levels in both are correct.
I was a little creative how I rechecked the DCT fluid which is a dynamic fluid change, compared to the differential which is a static fluid change. Instead of raising a cold car and running the trans up to the correct fluid temp of 60*C (140*F), I took the car out for a "hot" drive, Got the trans temp (on the dash) up to 185*F then pulled it in the bay, shut the engine off, connected the diagnostic tool and monitored fluid temps until it cooled back down to 60*C (backwards from the WIS process). Then started the engine with the car raised, shifted through gears, and then checked the DCT fluid levels. I had the slow run/dripping of fluid that I wanted to see, so happy to second check it. The differential gets checked statically, engine off, so that was simple and I was confident I'd see the correct fill there.
Something to share with those who will try this - I monitored the trans fluid temps with a diagnostic tool. The temps I got out of the transaxle did not agree with the dashboard trans temp. The dash temp was higher than the actual fluid temps and I think this is important. The wrong fluid temp will give you the wrong fluid level. If you use the dash temp, the DCT will be overfilled.
Here is a snapshot when I was watching the trans cool down after the drive, then a snap of what the dash was reading.
As the temps continued to cool down closer to the 140*F, the difference became greater. At 140*F, the dash was still showing 161*F. After restarting the engine, the dash gauge did not change, but my scan tool started to jump around a few degrees which is representative of the fluid beginning to circulate through the cooling lines. Can't explain this except to conclude the dash gauge could be a lazy gauge. Some of these, like the outside air temp are designed to update more slowly than live. Just an FYI.
I had a couple of private Qs and sensing there is some misunderstanding how the DCT fluid change works, so I thought it would be beneficial to cover some of the Whys rather than just what to do.
On the differential, this is a simple (old fashioned) static fluid change -
Drain the fluid, replace the drain plug
Fill with fluid until the excess runs out - then done.
On a dynamic fluid change, the correct fluid level is accomplished with the gearbox in a running condition and with certain other conditions such as fluid temps while running. The reason this is done is twofold -
The correct fluid level can only be obtained with the fluid circulating though the cooling circuit; otherwise, in a static situation, the cooling lines drain back into the reservoir changing the level.
The second reason, basic laws of physics - fluid expands/contracts as its temperature changes.
Here is the WIS instruction. I've pointed out the salient steps here that are necessary to get this correct:
Red arrow - First step is to drain the old fluid (engine off), and measure the quantity drained. If correct, it should be about 5.6L (6qts). Then cap the drain and refill WITH ONE MORE LITER than drained off. So, you should be pumping in about 6 1/2 Ls. Remember you are doing this refill with COLD fluid, at least colder than the 140* it will eventually see where it will have expanded when the engine is running and fluid circulating though the cooling lines.
Green arrow - NOW you start the engine (follow the instructions) and the engine will NOT be shut off until the second green arrow; or, in other words, you WILL be under the car either on a lift or on jack stands with the engine running.
At the blue arrow - this is where the engine will run for quite a bit of time (took mine about 45 mins) to reach 60*C on my diagnostic tool, not the dash. During this time, if the fill plug is already open, the EXTRA 1 liter of fluid you added will be dribbling out (or if you cap it, will drain out all at once). Once the 60*C temp is reached, cap off the fill plug WITH THE ENGINE STILL RUNNING (very important).
Second green arrow - NOTE the engine is running all the way up to this point. Then you're finished!
Hope this helps some misunderstandings I was getting from Qs.
Acta, this is such an important post for those of us who do our own work on our GT’s
Acta, I cannot thank you enough for taking the time to document your process! I love that you reversed the process! After all, thermal coefficients of expansion don’t care if you cool or heat, it’s the change in temperature that results in the change in volume. Very smart to reverse the process to verify the full level!
I am reviving this thread BC I am PMing with another member and I want to include docs that I cannot put in a PM:
Attached please find my marked up copy of the WIS for transaxle oil change. This doc has some notes on the first page and in the margins that might not make much sense BC I've used it for a few different members and each time more was added. I have noted in the Margin the places where the DIFF starts and where the TRANS procedure starts.
Here is a pic of the replacement drain/fill plugs recommended to be changed in the procedure. They are replaced BC they all have an integral O-Ring built in that is not separately replaceable. The green O-Rings are visible in the pic. The special fill tool is shown with a piece of hose I have permanently fixed in the tool so I do not have to keep changing it. I found a very economical hand pump that works well for this op. It comes from Harbor Freight the pump and hoses are red. It is easy to find at HF, just look in the automotive section for the RED hand pump. Hoses in that kit are a good fit for the tool.
FYI - it takes 3 dash-717 drain plugs if you want to replace them all. There are two used on the rear compartment where the Spirax goes. and one in the front compartment where the DCT-F3 fluid goes.
Last edited by Acta_Non_Verba; 09-29-2022 at 07:05 PM.
Just a word of caution to DIYers, so there is no confusion with the fluid change on the 190 platform - there are some differences with this SLS procedure above and are not the same for the 190.
The entire first part about the parking brake does not apply to the 190. Make sure you follow the 190 WIS steps through the fluid changes and corrected fluid level steps.
Last edited by Acta_Non_Verba; 07-01-2022 at 10:41 AM.
18 AMG GTC and 22 F150 Limited. Past owner 16 Maybach, 17 Brabus Smartcar, 06 Ford E150, and 22 G70
ACta we have both done this job before and I can offer one bit of thought. If I were to do the job again I would SKIP a lot of the steps and simply add back into the trans the exact amount that came out. Now as you probabably recall I had to go back and add a little because of lurching when coming to a stop. This was ALWAYS the case with my car even before I changed the fluid. So in my case the fluid was not correct from the factory. But with someone that has a perfectly functioning trans I would just do the remove and reinstall the exact amount that came out.
Just so much simpler than the directions and all the leveling ect.
ACta we have both done this job before and I can offer one bit of thought. If I were to do the job again I would SKIP a lot of the steps and simply add back into the trans the exact amount that came out. Now as you probabably recall I had to go back and add a little because of lurching when coming to a stop. This was ALWAYS the case with my car even before I changed the fluid. So in my case the fluid was not correct from the factory. But with someone that has a perfectly functioning trans I would just do the remove and reinstall the exact amount that came out.
Just so much simpler than the directions and all the leveling ect.
Hi Katie,
I think an argument could be made for this under certain rare conditions. I would guess that is a possibility with a car that is never driven aggressively, garage queen type. However, I think the procedure was designed for more average/middle of the road use to aggressive to extreme use.
When you look at the change interval in terms of mileage/time I believe on gearboxes like these (all of the ZF transmissions too) there is some fluid depletion and the 1L overfill then allowing the excess to pour out at a given temp replaces that depletion to the proper volume.
On mine, for example, what was left in the trans at temp, compared to what was measured at the drain was net more volume. In my case it was about 8 ounces. I drive somewhat aggressively, but I don't track this car. Also, I changed my fluid short of the required mileage by about 1/3rd. So this is a defense of the factory procedure and it could explain why you might have been 10 oz short.
On many ZF transmissions I've done, which use the same technique, overfill with cold fluid, then warm up to a defined threshold temp, the new fill would always be more than the drain off.
Frankly, as dangerous as this procedure is for DIYs and on jackstands, I would rather see someone do just what you suggested than risk a running car in gear and launching off jackstands. Probably better measuring off a static drain then replacing same than nothing at all.
All the leveling I had to do was a big part of why I said drain and replace exactly what came out.
Hi Katie,
I completely understand. As a Mechanical Engineer with a fascination of the technical aspect of cars, I value my time understanding what other engineers were thinking when they developed certain procedures, (Maintenance, or with designs). For me it has always been not only the "what" (do I understand what to do), but also the "Why" (why did Engineers take this route, why are they prescribing this?). Once I can grasp in my mind the "why" I like to share that part with the community.
After I do, then the "intelligent" community (and I consider you part of the intelligent community) can make decisions to deviate from that process as you've analyzed and assessed best fit your individual needs. I've come to very much respect the expertise you have. It's obvious to me you know what you're doing and you'll make a decision that is rational to the circumstance.
18 AMG GTC and 22 F150 Limited. Past owner 16 Maybach, 17 Brabus Smartcar, 06 Ford E150, and 22 G70
Acta you are so kind. My first two years of college got me my aircraft mechanics certifications. That would make me one of the people that occasionally grumbles about engineers. Now my husband is an engineer and like you he very often thinks deeply about things. There are times when I have to remind him about the contest between the calutron girls and the engineers at Oak Ridge Laboratory.
Hello, I just completed this service myself. Another piece of information for those with the GTR model: You need to remove the rear underbody panel and all 3 diffuser bottom panels in the rear. There's a specific order that these pieces stack so I suggest taking some photos as you're taking them off. Another thing is that the GTR has a transmission damper which must be removed as it's blocking one of the drain ports for the differential (the differential has 2 drain ports). It's not entirely obvious but what I did was remove the side which attaches to the frame first, then push in the damper by finger until it can drop down the car towards the ground, then remove the two torx bolts holding the bracket to the transmission housing.
This was quite a project and I followed the WIS instruction to the t. For reference, on the transmission side I drained out 5.2L, added 6L, then drained more. I ended up with only about 200ml more in the transmission doing it this way.
Special thanks to Acta and Katie who gave me a lot of advice and answered many of my questions.
Hello, I just completed this service myself. Another piece of information for those with the GTR model: You need to remove the rear underbody panel and all 3 diffuser bottom panels in the rear. There's a specific order that these pieces stack so I suggest taking some photos as you're taking them off. Another thing is that the GTR has a transmission damper which must be removed as it's blocking one of the drain ports for the differential (the differential has 2 drain ports). It's not entirely obvious but what I did was remove the side which attaches to the frame first, then push in the damper by finger until it can drop down the car towards the ground, then remove the two torx bolts holding the bracket to the transmission housing.
This was quite a project and I followed the WIS instruction to the t. For reference, on the transmission side I drained out 5.2L, added 6L, then drained more. I ended up with only about 200ml more in the transmission doing it this way.
Special thanks to Acta and Katie who gave me a lot of advice and answered many of my questions.
Hi RWA,
Glad it was successful for you!.
BTW, the damper is common on all models. I remember removing it on mine too which is not a GTR. Good that you mentioned it here and hopefully it will help others.
Yes, as per the service manual. You can check the other thread for PDF of all services. It certainly needs to be done, I did mine at 10k miles 4 years, see how dirty the gearbox oil is compared to new.
Yes, as per the service manual. You can check the other thread for PDF of all services. It certainly needs to be done, I did mine at 10k miles 4 years, see how dirty the gearbox oil is compared to new.
Difference is huge. I am thinking to change mine earlier than per service guide. 23k km odo , 3 years. Do you think it’s worth it? or shall i wait for recommended period.
Regarding service pdf file, can you please link me to it ?
I'm attaching the PDF here. Yes, you can definitely do it earlier no need to wait. Mine was only at 10k miles. I did it because it hit 4 years but more importantly I track the car.
Difference is huge. I am thinking to change mine earlier than per service guide. 23k km odo , 3 years. Do you think it’s worth it? or shall i wait for recommended period.
Regarding service pdf file, can you please link me to it ?
Hi Dav461,
These are good questions you are asking. It makes a good opportunity to add a little more to this thread for posterity. The chart below shows the different applications where the Getrag 7DCL750 is used. This is an older chart that starts with the introduction of the AMG GT/S versions. Add to this the rest of the AMG GT family. Of the three manufacturers, the Ford GT application is the closest to the AMG GT/S with all of the gear ratios the same.
Interestingly, all three manufacturers use a different maintenance schedule:
AMG GTs use a 4yrs/40,000 miles change interval
The Ford GT uses a 6 year/30,000 miles:
The Ferrari has NO fluid change schedule, just a periodic fluid level check. Since the schedule isn't published by Ferrari, references to the change, or lack of it comes from one of the Ferrari forums. Here is a screen capture from an owner:
On Ferrari, their approach seems to be the old "seal for life" philosophy that the ZF transmissions used to use. On some Ferrari forums, users talk about their dealers offering to change fluid if the customer requests it. Probably those who really use the car might request the fluid change. Other than that, Ferrari kinda just lets it break, then replaces the whole transaxle.
On all of these applications, there is little talk about losing friction clutches, but more failures with contaminated sensors, etc.
Hope this helps with how you decide about your change interval.
Best,
Acta
Last edited by Acta_Non_Verba; 09-01-2022 at 10:32 AM.
Hope this helps with how you decide about your change interval.
Best,
Acta
Hi,
According to my local dealer there are two types of oil is used 236.25 & 236.26 , both can't be purchased in 1L&5L cans, only 20L. Is that correct ? Bevo shows Shell TF DCT-F3 & Shell SPIRAX S5 ATE as a substitute for 236.25 & 236.26 respectively . First one also can not be purchased in 1L & 5L capacity.
Hi,
According to my local dealer there are two types of oil is used 236.25 & 236.26 , both can't be purchased in 1L&5L cans, only 20L. Is that correct ? Bevo shows Shell TF DCT-F3 & Shell SPIRAX S5 ATE as a substitute for 236.25 & 236.26 respectively . First one also can not be purchased in 1L & 5L capacity.
Hi Dave,
The transaxle has two compartments - One holds the 236.26 which is a GL5 gear oil. Think of it as the differential side of the transaxle. The other compartment is the dual clutch transmission side and uses the 236.25 which is a DCT-F3 trans fluid especially formulated for the clutches.
Both of these fluids are produced by Shell Oil company and the only brands MB approves for use in the 7DCL750 transaxle. Other off-brand products might, or might not work, but the gamble becomes yours.
I'd be a little cautious using off brands and wouldn't do it if it were my trans, but I'm also aware these two products are nearly impossible to find. I especially wouldn't do the Redline. Also, these oil companies are selling oil, so if you ask them how often to change the fluids, their answer is going to support selling more oil.
Here are the two specs (236.25; 236.26):
Both of these products are available in 1L Bottles, they're just almost impossible to find. The dealers buy the fluids in bulk sizes such as 20L or larger containers and why you are seeing that going to a dealer. They won't carry 1L bottles unless they see a marketing opportunity and most owners won't be DIYing this.
I purchased the 1L sizes but again extremely hard to locate right now and don't know if/when that will improve. Here is the Spirax I bought:
One last warning to be careful with off brands.
Hope this helps,
Acta
EDIT: Looks like while I was replying you edited your post and took out the parts about Motul and Redline, so parts of my replies might not make much sense.
Last edited by Acta_Non_Verba; 09-14-2022 at 06:49 PM.
03-11-2022, 07:25 PM
