cocobeex

This will be my first time doing Transmission oil change on my E by myself. (Before i let dealer do it)

Most people drain ATF from Transmission oil pan.
But I have seen some people draining ATF from Torque converter.

If i only drain ATF from tranny oil pan, will ATF in torque converter also get drained ?

I would love to learn what is the differences drainning ATF from torque converter and tranny oil pan.


All educational answers are greatly appreciate it!!!!!!!

kajtek1

both

sturitter

Draining the pan will not drain the torque converter and draining the torque converter will not drain the pan. Normal MB servicing drains both. The transmission actually pumps oil into the torque converter.

Stu

cocobeex

You meant drain from both ?

cocobeex

so, ATF has to be drained from both Torque converter and Tranny oil pan.

As you said Tranny actually pumps oil into TQ conveter, So, that means only need to fill up ATF from Tranny oil pan fill hole, correct ?

s140s

When you refill the pan, ATF will be pumped into the torque converter, there is no pan fill hole, it needs to be pumped via the drain hole. Basically you should measure how much is drained, refill with .5 to 1 qt more than drained, start the car and monitor ATF temperature until it reaches 35-45C, then you remove the drain bolt and extra ATF will drain through overflow tube. When it starts dripping, you reinstall drain plug and call it a day. All this is supposed to be done with engine running and vehicle leveled.

cocobeex

Thank you very much for the details.

All this needs to be done while engine is running, Do I put it in N ? or P ?
Thanks!!

s140s

Engine on is for correcting fluid level, you add about 9 liters of fluid, go through all the gears, then wait for fluid to reach temperature. Once it reaches the temp, with the Engine on and trans in Park, remove the drain plug/plug fill adapter and let excess fluid drain. Reinstall the drain plug and its done. Here is a more detailed tutorial.

https://www.benzworld.org/forums/w21...7g-tronic.html

MrNice

I was wondering about this so you can actually fill the entire amount of fluid first and simply start the car.. go through the gears.. wait for operating temp then let all the excess to drain? All the videos seem to show only putting in 4 liters first then the remaining after it is hot... and i'm not sure why.

S-Prihadi

The initial 4-5 liters as first step before final top up, I am guessing is not to over filled the tranny oil pan....where the torque converter was still empty when it got drained.
TQ itself takes approx 3.5 liters. So in theory the oil pan will hold maybe 5.5 to 6 liters max and TQ at stand by has 3.5 liters.
It takes approx 9.5 liters on my tranny with AUX oil pump, for ECO S/S version.

MrNice

oh ok this makes sense. When you start the car is fluid automatically sucked into the tq converter or does this happen when changing gears? I also noticed in this video he let it sit in park until it reached temp then turn it off. I’ve not seen this method. Most turn on the vehicle and immediately go through the gears.

S-Prihadi

I believe the moment the engine is started and therefore tranny starts to spin , the torque converter automatically gets oil into it.
The gear changes procedures would be more for small oil galleries where the solenoids are the one controlling it, to be properly filled with oil.
Gear change in our 722.x tranny is done by hydraulic command/actuation, oil pressure and volume based, hence solenoids are the one doing it

MrNice

I had read somewhere that when you install a new torque converter they come with a warning saying to put a quart (or more) of oil in them before installing them. I can't help but wonder if the same is true when you drain the torque converter. Is it possible to put fluid into the torque converter via the drain hole.. I know it comes out very slow.

S-Prihadi

When a torque converter is not new, aka has been installed on a car, its lock up clutch is already wet and draining it won't be as dry as a virgin
brand new TC from the store. So you need not worry...it is sort of pre-lubed already.

Also a TC is a fluid coupling, no oil in it.....it wont spin. So it is safe.
TC internal Lock up clutch wont be engaged anyway during engine start-up.