2016 E350 Transmission Service - No Torque Converter Drain Plug
 

Hi Folks,

New member here. I performed a transmission service on a 2016 E350 with the 722.906 transmission. This vehicle was RWD, has start/stop and has the external auxiliary transmission oil pump. Prior to servicing, I checked the MB EPC and the diagram shows this vehicle to have a drain plug on the torque converter.

After raising the vehicle on the lift and removing the external auxiliary oil pump, I found a round access hole at the bottom of the bellhousing (see picture below) and a small square access hole on the passenger side of the transmission bellhousing (covered by a rubber plug, forgot to take picture)). I personally rotated the engine multiple times (27mm socket on the crank pulley) and was unable to find a torque converter drain plug thru either hole. When you look thru the round access hole, all you see is the bottom of the torque converter. I saw a couple of welds that looked like a drain plug may have been intended for that spot, but no drain plug was ever found. The square access hole on the passenger side of the bellhousing only lets you view the teeth on the flexplate and no drain plug was found there either.

Since I was unable to find the torque converter drain plug, I performed a traditional pan drop and filter change and removed almost 5 quarts of fluid (see picture). While not ideal, this is still more than 50% of the total fluid volume (unit holds 9.5 quarts) being replaced.

Has anyone else experienced this issue? I called 3 local MB dealers and all of them told me they do not drain the torque converter. I also asked one independent Mercedes specialist and was advised that the most recent 722.9s no longer have a torque converter drain plug.

Thanks!https://cimg7.ibsrv.net/gimg/www.mbw...880644da5f.jpg
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I've checked many of the transmissions and torque converters over the past many years.. Some cars have them, some do not. Like you, I also prefer to drain it all if there is a drain plug, but there are a lot of the newer cars that just don't have a drain plug to mess with. Even some of the cars I did find a drain plug on, I couldn't locate the new crush seal in EPC and had to reuse the old one or find something that would fit.

To my knowledge, the info you got was right, MB stopped installing drain plugs in the converters but has left the access ports in the housing castings.
Jealous of your lift!

Hang on....

I was told you couldn't perform this service on your own because you needed the dealership's STAR computer to reset the CEL or something that you get after doing it. Or something like that.

I have a '14 E350 4Matic. Can I change my own trans fluid? I'm fairly certain I have the 722.9 trans.

you can change it yourself, i have faith in you.

Shops are using SD to read ATF temperature, but infra-red thermometers work as well. My cheap OBD plug with TorquePro shows ATF temp, but it seem to be bogus as it is changing only by few degrees.
Anybody knows for sure the advised temp for final level checking?
I hear 45, than 50 than 80C.
Also how about valves cleaning ?

If I remember correctly from the last time I looked it up, the vehicle obviously needs to be level and you should be starting from a cooler point. Also, you don't want to do a quick transmission service on something that you just drove 30 miles in. The fluid temps will remain too hot and high for a while. As for the temps, it should be 45*C or 113*F for the 722.9 transmissions. There was a small change in those numbers if you didn't have the updated transmission pan, but most of those should have been changed out since then.

I used an Autel Maxisys Elite. It has a guided function for the fluid level check.

Yes, the level check needs to be started at a lower temp, preferably below 35C. On this car, I believe it sat for a few hours before I did the trans service. I performed the level check at 45C.

Since my previous reply in this topic I serviced 2 of my 7G transmissions.
Both of them had converter plug, but when in 2008 model the access was at the bottom, on 2014 who has servo at the bottom, the access is behind cover placed at like 5-o'clock.
The infrared thermometer wasn't too convenient as transmission was showing several degrees differences in different points ,what makes big error margin.
I believe all 7G have converter plug, so keep looking.

Does your 2014 have start/stop? The models with start/stop have an auxiliary oil pump and I think those transmissions are a bit different.

I recently did a 2010 C300 and a 2012 C250 and both had the torque converter drain plugs.

Yes. From what I heard all lifted W212 have ECO stop. Did not have to work on engine too much, so no idea about aux oil pump, but as I said, with transmission park servo the access cover on bell housing is moved to the side.
I noticed that on ML the converter plug has to be access via very small hole in framing, so we might have lot of variations.

When I change trans fluid in my truck, I do the pan drain, clean and replace the pan, and fill with fluid. Then I pull the return line from the trans cooler in the radiator to where it dumps back into the trans and run a clear hose into my dirty fluid container. Start the car, let it run for 10 seconds, stop engine, make sure you have enough fluid, start again for 10 seconds, stop engine, check fluid, etc, etc,etc, until you have new, clean fluid returning from the radiator cooler. Then fill to capacity, check temps, etc. So not only do you get the converter ATF replaced, but the lines to and from the cooler as well. Sure would be nice to have a lift to do this to the Benz!

I don't know if my 16 E350 even has a cooler in the radiator, but assuming it does, wouldn't that be an option to get as much fluid exchanged as possible?? Definitely more than what a dealership would accomplish.

You will never get 100% flush. I did the refill and power flush couple of times and even running double the amount of ATF, you still will have color change after driving some distance (unless you start with clean fluid).
Than, driving high mileage MB, I believe several of them had factory ATF running well over 100k, when I think 1 of W210 run over 200k on factory fluid as open pan uncover some goo ATF turned into. When new fluid smoothed shifting, the transmissions never had ill symptoms.
So if you really have no plug, I prefer opening the pan, dripping it overnight and just refill, what will get all the heavy contaminants and about 70% of fluid exchange. You can always do it again 30k miles later.
Running 20 l of MB ATF is not cheap for small additional benefit.

Mercedes pumps out from the top, no more need for drain plugs on TC. If has been this way for at least the last 10 years..

Since you have some experience with this process, please tell me if the return line from the radiator to the trans would be easy to get to and to attach another plastic drain tube.

The connections changed over the years.
Older MB transmission coolers were hook up using hoses with flare fittings. Those are easy to access, disconnect and reuse.
Newer models do have solid pipe that enters radiator with sealing oring.
Those are harder to access, will not bent easy and darn orings like to leak after reuse.
Check what you have and evaluate.