722.6 Torque Converter (Part Number A2112500902) - Disassembly Photos

[rich.g.williams]

I have been trying to fix my 722.6 5G-Tronic transmission recently. My strategy is to disassemble, inspect and test everything. I reached a point where the only thing I could not get inside to inspect (and I could not rule it out as causing my fault) was the Torque Converter. I had already bought a second (pre used) Torque Converter but with both of them in front of me I could not decide which of the two to put back into the car. I tested and compared both of them as much as I could (and the lock up clutch worked on both of them) and couldn't find any issues. There is a Sprag (freewheel) inside but I couldn't test it or feel its presence on either Torque Converter.

So working on the basis of "better the devil you know" I decided to fit my original Torque Converter back into the car and cut the other one in half. The idea being to make my own assessment as to whether the fault was likely caused by the Torque Converter.

Having seen the components and quality of build inside everything looks very strong and built to last inside the Torque Converter. I'm attaching the photos I took this morning.

 

[rich.g.williams]

More photos

 

[rich.g.williams]

Just to mention that the Sprag (freewheel clutch) turned out to be working fine when I tested it again this morning, the Lock Up Clutch Rings look as good as new. There were three O rings inside (two are the clutch piston seals and they all looked fine).

I found some sediment inside. There is a flat bearing inside not shown in the photos (I didn't take a photo of it) the bearing was fine. There is a heavy spring assembly (not clearly shown in the photos presumably to take out axial or rotational shock. It all looked fine and is very well built. I could not find any signs of damage or wear to any component inside.

I have read (and seen videos) where it is suggested that ATF cannot escape from the Torque Converter Lock Up Clutch piston or worse ATF can "leak" from the main chamber in the Torque Converter into Lock Up Clutch piston. This cannot cause a problem (unless there was a gross issue) because when the Lock-Up Hydraulic Valve moves to take the Torque Converter out of Lock Up it vents the piston ATF to sump. Therefore that hydraulic valve will act so as to pressure the Lock Up clutch as commanded by the Lock Up Solenoid come what may (hopefully).

I also read that centrifugal force can increase the Lock Up piston pressure but this is only really likely to do anything if the engine RPM is high (before the piston has had a chance to vent to sump). I'm guessing that a little bit of Lock Up at high engine RPM is unlikely to be an issue.

The geometry of the Torque Converter makes it very difficult to get all the old ATF out. When I split it about 30% of the ATF was still inside. Some videos show it being blown out by compressed air but even that is not going to get it all out. There is no way I would risk drilling a hole for a drain plug. Perhaps the only thing to do is fill it right up with fresh ATF empty it again and repeat two or three times, very wasteful of ATF.

 

[AMGeed]

Well done on tackling the job yourself.
Way beyond my skill set.

 

[rich.g.williams]

Well done on tackling the job yourself.
Way beyond my skill set.

Thank you, just thought I would post some information (that's not well covered elsewhere) because good posts by others have helped me a lot over the years.

By applying a principle called "diagnosis by disrespect" nothing Mercedes ever goes wrong because there is nothing that Mercedes make to disrespect

I'm sure you could tackle such work given time to study the job and time to do the work.

 

[Wighty]

Those pics are modern artwork , they wouldn’t look out of place in a gallery .
Some look like ammonite fossils

 

[rich.g.williams]

Those pics are modern artwork , they wouldn’t look out of place in a gallery .
Some look like ammonite fossils

Lol the Ammonite fossils occured to me also.

Getting technical again how TC's work is far from obvious to me but I realized that the two halves enclose a toroidal tube so I presume that the ATF spirals around that toroid, makes much more sense having realised that.

 

[rich.g.williams]

Something about the Torque Converter (TCC). There are three mechanical couplings between the TCC and the Transmission:-

1. The outer shaft from the TCC engages the ATF pump, so the pump is always running with the engine.
2. The middle shaft from the Transmission into the TCC, this never turns, it is solidly attached to the Transmission and to the TCC Stator (via a sprag/freewheel)
3. The inner shaft is driven by the TCC Turbine and is the input shaft to the transmission. The Impeller is part of the TCC case and turns with the engine.




There are three O rings inside the Torque Converter, only one of these can be replaced without splitting the TCC, the small O ring shown below. The other two O rings seal the TCC Clutch Piston.






-

 

[rich.g.williams]

Photos of the Torque Converter O rings. The small Transmission Input Shaft O ring can be replaced without splitting the TCC. Difficult to replace but it can be done.












-

 

[DREAMER NO2]

This might come in at some time https://at-manuals.com/transmission_tax/mercedes/

 

[rich.g.williams]

This might come in at some time https://at-manuals.com/transmission_tax/mercedes/

Thank you. I never saw the 722.6 repair book before, its in Russian but its still useful for the numerous diagrams given.

 

[DREAMER NO2]

I can read it no probs . Not in Russian to me

 

[rich.g.williams]

I can read it no probs . Not in Russian to me

Could you send a link to the actual document please? maybe I'm looking in the wrong place.

 

[AnthonyUK]

The actual document says it is in RUS language.

Download manual repair book 722.6 (RUS language)

 

[rich.g.williams]

Yes that's the document I downloaded from your previous link. I can't read the written text but still very useful for the vast number/numerous diagrams given. Towards the end it has a few very useful diagrams showing how the B2 brake is controlled and it shows exactly where the valves are in the valve body - very useful because its a different perspective on similar information. It uses the same nomenclature as MB wiz does so I know what's being referred to.

So if you can read it does that mean you are Russian or a fluent Russian scholar?

Someone has gone to a great deal of trouble to compile all that information. Its obvious that the original MB documentation used a mathematical nomenclature for the entire 722.6 design but very little of that is published anywhere I can find.