I finally had some time over the weekend to do the transmission service. I only replaced the fluid in the pan, did not drain the TC. More on why I opted for this instead of the flush later.

Some details about the car: 7G with red fluid. I used Fuchs 4134 (red). Last tranny service was done around the 66000 KM mark. Current mileage 157700 KM.

Some of the challenges I encountered. I am sure none are new (others have run into them), I just wanted to note them.
Removing the guard panels was a little bit of a challenge. The two bolts which hold the front and middle panels did not want to come out, neither did the rear two bolts for the middle panel. It turned out that the clip nuts for all four bolts had managed to snap and the bolts were free spinning. I had enough space to anchor the rear two, but not the two in the middle, so I cut them.
Once the pans were down, leveling the car was "fun". I was doing this solo. I have a slightly sloped driveway which added extra joy to the party. After countless times of going under the car, getting up, going under, getting up, and on, and on, and on, you get the idea, the car was level. Draining the fluid was easy. It made an impression on me that it was rather clear. I expected darker brown, maybe black, considering the longer run between changes. Dropped the pan and noticed that the lowest surface was nice and clean, but the beveled plane where the magnets sit was covered in a black muddy substance. The magnets were covered in the same muddy substance. I'm guessing lots of tiny metal shavings combined with fluid. Cleaned up the pan/magnets and reattached with new gasket and filter.

Considering the mileage and that the old fluid was in such shape plus the pan's bottom was also clean, I chose to skip draining the TC. I'll give it about 10000-15000 KM (two to three years of driving in my case) and have a go again. If the fluid is still rather clean, I'll flush then. I'll be very interested to see the state of the magnets.

As I was reattaching, I noticed that I had not replaced one of the pan bolts. I could not tell easily which one it was, so I opted to keep going. Well, the old bolt snapped on me when I was torquing it. Add some hearty and healthy blessings pointed towards the bolts and generally working on older cars, which were heard by the AirBnB guests next door. Removing the bolt was not difficult, I was able to turn it by hand without removing the pan. So, anyone reading this, replace the bolts, as recommended, and save yourselves the blessings outbursts and extra work.

Filling the tranny was easy. I have a cheap 12V reversible pump. I drilled two 3/8" holes in the cap of one of the Fuchs 5L bottles. Caps for the 1L bottles are the same size so you can reuse it. The air hose needs to only go past the cap, but not submerge in the fluid. The fluid hose needs to be submerged in the fluid. I added enough length to the fluid hose to go to the bottom of the bottle. I sealed the cap with hot glue. Give the hot glue enough time to harden and make a good seal around the hoses/cap. I also had the attachment to the tranny pan, plus I added a 1/4 turn ball valve to minimize unnecessary fluid waste/return. I had to use gravity as well as pressure, so if you are doing the same as me and your air source is weak, don't despair. Lift your new fluid container above the transmission and let gravity do its magic. I just propped the bottle between the hood and windshield. If you have a compressor, you would be fine. Maybe next time I can rig the Airmatic compressor to fill the AT bottle LOL just kidding!

I drained a bit more than 4 L from the transmission, around 4.5 L, so I added 5 L, ran the motor for a bit, switching between P/R/N/D, and mixing the order. I closed the valve as there was no fluid movement (clear tubes made it easy to monitor) till the temp was 45C/113F. I measured temp with MM (it has temp setting and sensor), which I have used before and it is accurate. I also have an MB II, but I did not bother with it this time. Once temp was reached, I disconnected the tube between the valve and bottle and opened the valve to let the excess fluid drain. I have not yet measured how much was dumped out, but I'm judging about 1/2 L. Plugged the pan and turned the car off. That was that! The rest was packing up tools and lowering the car, just as it started to rain.

Update: accurate volumes added to this post
Old fluid drained: 4.2 L
New fluid pumped in: 5 L at ambient temp/motor off
New fluid returned: 1 L at 45C measured on the pan with MM

The two short drives since doing the fluid change have been uneventful. I feel that the transmission seems to change gears tighter. That's just my butt dyno, though. Sometimes it's accurate and sometimes it's not, so take that with a grain of salt.

Leftovers to do:
- clean and paint the guard panels. They are metal and there is some rust here and there. I also had some rust on the pan, but it was superficial and will last another 2 years till the next tranny fluid party.
- source two bolts and four clip nuts.

 

Well done! Some questions.

- what year is the vehicle?
- what did the dealer or Indy quote you for this job, if you got a quote?
- is the 164 platform a fill-to-overflow procedure?
- do you have the off road package with two speed transfer case? Question prompted by your comment about the metal belly pans.

 

Nice work expl0rer!

I recently did mine as well (plus torque converter) but used a very different technique to measure the refill.
My x164 had it's last transmission filter/fluid service done by the MB Dealership, has no leaks, & operates fine, so I proceeded with the assumption that the current fill level was correct to start. After draining all trans fluid, I weighed the total collected with an inexpensive but accurate digital scale. (Collected a total of 7.960kg)

Then I simply filled until I had put exactly that amount back in.

I know it sounds strange to take this approach, but there were several factors that made me feel like it was more likely to get consistent results than the usual method.
1- Leveling: When you actually look at the underneath of our vehicles, there is some question in my mind as to what IS level exactly? Some say adjust the car to that the flat part of the trans fluid pan is level (btw that seems wrong when I tried it) others said "use the frame", others say make sure the ground is level and then use 4 identical jack stands with the same height setting, etc. Almost any way I looked at it, there was a degree of uncertainty in my mind about what is "level".
2-Temperature: Fortunately you have a scanner that gives the transmission temp sensor reading. I don't have that, so the methods available to accurately measure temp leave room for error. (Infrared thermometer (#No!), Digital Temp probe with thermistor, etc)
3-Overflow tube length, and fitment, etc.

I could probably go on for a while about all these things but using the unorthodox method I did, gave me compete confidence that I at least put back in the exact same amount of ATF (by weight) that was in there before I started.

I only mention this in case it helps anyone else. *** It's not a suggested method****

Great results! My wife & I both think the transmission seems to run and shift slightly better than before. That could be in our heads tho...

2008 x164 GL450

 

2010

I did, last year. IIRC, the dealer quoted $600 CAD for the same job I did - drain fluid/replace pan/gasket/refill fluid. I did not ask for quotes about flush or TC drain and had planned to do a flush, but changed my mind when I did it yesterday, for the reasons I noted.
Yes, it is. I followed a document I had found (most likely here somewhere) and saved, which documented the process very well. I have uploaded it here, but can't take credit for writing it. I am not even sure if the person who wrote it had an X164 or another MB, but it is for the 722.9 transmission.
I do, the metal underpans were standard on the vehicles with the offroad package.

 

Great points! Thanks for sharing!

I sort of did the same as you, but by volume rather than weight, in addition to leveling the vehicle. I did measure what came out vs what went in (and some of that new fluid out again). I used the pan surface for level. It made more sense to me to use that, rather than the frame, because you can have worn mounts or bushings which could affect the relationship between the pan and frame. Assuming that the two are supposed to be leveled to start with, and with good bushings/mounts in the first place.

I think the MB engineers have built in a "safe range" of fluid volume in the transmission's design. I can't imagine that each and every transmission will have the exact same amount of fluid to operate optimally. Let's say, the range was +/- 3%, that's 0.270ml times two or 0.285 QT times two. The 722.9 fluid capacity is 9L or 9.5 QT. That makes a little over half a litre or quart. That is quite a bit of variance in fluid volume. I think that if you're within the safety range, all will be fine.

One of the reasons I think this way is that the procedure says to open the drain at 45C and let fluid drain until a little is still spilling out. "a little" leaves a lot of room for interpretation. Having done this personally and also having seen enough footage of transmission services for a lifetime, that "splash" will be there for some time, so after the initial drain I can have the car running for 10 seconds or a minute and the amount of splash would be similar. And you can't expect that two mechanics will have the exact same reaction time to plug the drain hole, or even the same mechanic doing it exactly at the same time over two services.

I haven't had my wife in the car since the fluid change, but she will definitely feel any differences and let me know. She's the backup butt dyno (dynamometer, not dinosaur) in the family.


Edit: I forgot to add that I did not use the MB II scanner to check temp. I could have but opted not to, as it would have required another up/down. I had enough of those already. I did not want to get my oily hands on it, either. The multimeter I have tests for temps so I taped the sensor to the pan and watched it climb slowly under the car.

 

I had some interesting observations yesterday. I compared the MB II transmission temp and the MM temp gauge. There is a difference which progressively increases. At 45C/113F reading with MB II, the MM temp is about 10F lower.

MB II displays the temp increase in increments of 1 degree C, but in F it is about 2 degrees F. This makes me question the accuracy of the reading on the MB II or the sending unit used by the scanner. Is the temp change when the fluid reaches that temp? Or is half a degree before the actual temperature. In other words, is there any rounding up?

I noticed that the MM temp is different on the pan when measuring on the rectangular sections vs the valleys. Think city map where the rectangular sections are the city blocks and the valleys are the streets. The valley temps are slightly higher (approx 2-3F) than the rectangles.

If both are accurate, there is a significant delta in the pan surface temp vs. fluid temp. This, assuming the sending unit is measuring the fluid temp and not some surface temp inside the transmission. I am unfamiliar with the sending unit used for the fluid temp. I should expect that the outside surface of the pan does not get heated up as fast as the inside and the fluid would be slightly warmer than the inside surface. And the fluid should be slightly warmer than the inside surface. Unless, of course. operational temp is reached and maintained for some time till the metal surfaces can match the fluid temp. I did not wait for that to happen when I test measured the temps yesterday.

Now, the kicker. When I measured the temp during the job, it was on a rectangle. The delta between the fluid and pan surface would be greatest. The new fluid which the transmission spit out at 45C/113F was 200 ml less than the old fluid. Yes, I have more fluid in the transmission now than before the service.

Here are the accurate numbers (I will update the original post with these as well)
Old fluid drained: 4.2 L
New fluid pumped in: 5 L at ambient temp/motor off
New fluid returned: 1 L at 45C measured on the pan with MM

So what does this mean? I did not have "enough" fluid in the transmission before I performed the service? I have debated pumping in another litre of fluid but this time let it flow out using the MB II scanner temp reading. But I am not convinced it will do a whole lot. If anything at all, I expect less than a litre of fluid to come out, as the fluid temp should be lower than when I measured temps on the pan and pressure in the transmission would be lower. There is a 50/50 chance that I am within the safe range, or under/over it. Only one way to work it out - flush fully and refill with 9L, but I am not doing that at this point. Considering the transmission shifts feel smoother, I will let it be for the time being and monitor transmission performance. Unless someone has a compelling argument to pump a litre of fluid in and release using MB II temp reading.