S-Prihadi

Gents,

For the 10 year all rubber and plastic replacement program I am preparing, transmission internals has come to my attention.
So not only the trans oil cooler pipe-hose assy I will need to replace, inside the valve body + conductor plate, so many o-rings existed
I am automatic tranny stupid, aka never touched its internal..... only DIY oil and filter change so far.

Mercedes only sell two items which has o-rings for conductor plate + valve body assy.
Other o-rings I need to source from aftermarket tranny re-builder.
These are the solenoids (8 of them ) o-rings :
https://www.newco-autoline.de/index....A-SUK-722.9-SO
or
https://www.klaus-automatikgetriebe-...et-kit-o-ring/
or
https://maktrans.net/A-SUK-722.9-SO

I have to check with them the material of the o-ring used, it has to be ATF compatible.
Even if wrong o-ring material is used, the failure will take years and not immediate, that is the problem.


or

https://blog.parker.com/site/usa/det...ssion-fluid-us



Start at minute 30:00


Here is what stressed me out:

01. The 2 magnets on the oil pan are to catch ferrous metal, they work good.
On the other hand this is also a bad news, that means the oil contains metal which can short circuit a connection , if the oil cleanliness is not maintained.
For oil cleanliness mine is clean enough for sure, albeit I drive my car hard and the traffic jam in my city would result in more low gear acitivies where engine torque is
at higher level due to reduction gear in tranny and hence technically the clutch pack will work harder. I am on a 2 years or 20,000KM oil and filter change for tranny, which
in actuality it will be a 10,000KM only in 2 years.

Here is the so called Conductor Plate. Observe the electrical contact points (2) per hole of the solenoid.

















The normal metallic "dust/grime" caught on the magnet is usually very fine one, like below :




If a tranny has metallic debris as bad as below....hhhmmm.... pray for your wallet.



will continue.......................

S-Prihadi

This is a good general animation for tranny oil journey


Our 722.9 valve body is typical valve body having 3 layers.
So oil goes from layer 1 plate ( bottom ) to thin plate or intermediate plate no 2 and then to player 3 plate (top) and then come back to bottom plate, depending on what
the tranny computer wants to do.




.
The tranny fluid must pass thru steel or plastic ***** and mini strainer with check valves, just like the ATRA video shows.







.

This is where a recent purchase by a 2nd or 3rd owner of a used car of say near 100,000 miles and 8-10 years old and the tranny never get proper oil change + filter at least twice or better 3 times by those earlier owners, can suffer big time paying the lazy sin of those earlier owners.

Looking at the valves clearance to the bore, metal to metal precision machining without any seals is what they use for fluid flow control, tranny oil cleanliness is no 1 requirement.





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The valve/s is/are the one controlling not only flow but pressure reduction from the line pressure of the oil pump to 2 type of reduced pressure duty.
So its not a simple OPEN-SHUT valve only.

This is a 5 speed 722.6 5 speed but the oil pressure reduction is the same as 722.9 7 speed.



If we believe o-rings in this hot fluid can last super long above 10 years and be healthy a 100% in terms of zero leak, duro-hardness and whatever aging an o-ring , we must be dreaming.
If the tranny fluid management is expected to do well for best shifts and whatever the design goal of the tranny in terms of driveability, comfort and whatnot......
these o-rings deserve proper attention/replacement at a specified interval.

Tearing open the valve body for cleaning seems to make good sense too, too bad it is rather complex piece of equipment.

Bottom line is, replace your tranny fluid more often is always good, given that you are lucky doing that from brand new car or have got a used car with proper maintenance or like me,
got the car when it was only near 4 years old and only 10,000KM, 1 owner and that tranny oil I replaced asap and it does good immediately.
Amazing, 10,000KM only but near 4 years old can age tranny oil to the extend the modulation is kinda dumb and slow. No harsh gear change or anything of that sort.

CaliBenzDriver

I admire tranny doctors that can unpack the hundreds of parts inside a gear box, diagnose it before reassembling it confidently.
These things are like mechanical computers 👏

I used to believe the solenoids were switching the various clutch packs between the converter and output shaft... Actually the TCU pulses the solenoids that gradually drive the piston valves that manage high pressure ATF. Solenoid only see enough pressure to counter valve return springs, not line pressure.


valve body pressure actuators return springs

Lucky us these valves are pistons that dont use O-ring seals. They are tight in bores.

Tranny oil has a tough act to lubricate bearings but not prevent clutches from grabing under pressure.


> TCC Shudher beware !!
I recently learned something interesting to prevent wasting our TC.

Our 722.9 comes fully refined with a killer partial TC clutch lock.... actually it should be called TC clutch slip - - You dont want to drive E-mode around town to prevent busting your TC. Drive the S-Mode to prevent that clutch from being called. E-mode is best for freeway.

Once the shudder shows up, TC is good to go!
It just get warped like overheated brake rotors.

The clutch friction slippage puts out a tremendous amount of heat inside tranny that gets cooled at radiator.

We know brake pad friction put out a lot of heat, clutches are their cousins: friction grabing steel plates.

Enjoy your time in Bali

S-Prihadi

The 722.9 if PLUS version ( 6th generation ) is different from non Plus version ( 5th generation ) for how the Torque Converter design is...
https://www.transmissiondigest.com/7...on-six-part-1/

So TC slip is less on a PLUS version, the blue ATF one.

===add=====




Oops, see the footnote : exceptions M271 EVO and M276
The list shows M276LA means turbo version.
Does this mean M276 NA get different torque converter ?

S-Prihadi

Here is a bad news :





Believe it or not, 722.9 even PLUS version has no oil pressure sensor.
Its all documented and hence software "calculated" during initial bench test and programming of the conductor plate brain, the TCM we call Y3/8n4
So it started with everything perfect, clean oil and all solenoids + valves zero leak.

The only sensors available are 3 speed sensors, among them are the input speed shaft speed and output shaft speed, to see/calculate the slip.
Its like not able to monitor the process, but able to see final result.
I think if in a generator US version, its like only having the frequency meter to see the 60Hz at the gennie/alternator side,
but the diesel prime mover side for coolant temp, oil temp and yada yada, is all calculated.
This is not new for MB, that is how they calculated oil pressure and oil temperature too for our engine.....based on initial dyno/bench test with virgin oil and
all mechanical components being healthy.

The tranny adaptation slowly build up its database as parts started wearing out, hence solenoids can not be misplaced during teardown and new solenoids
need to relearn. Still , in my thinking, why MB save small money when other automatic tranny can have up to 6 pressure sensors, example is Honda ...probably made by Aisin I guess.

Here is another cheapo fact : Come on, a year 2003 or later product, and they are so stingy on memory chip ?

If we do not know that DTC is limited to 16 only, and then the trouble produced more than 16 DTC, we may end up getting confused as to why new DTCs appeared after certain repair and not before the repair...LOL

MBNUT1

Thanks for sharing this info. Very interesting.

CaliBenzDriver

Master Surya always follows his own principles to dig up singular research material and turn up the best nuggets.


His itchy hands have transformed many machineries with applied sciences.


My lemon would not be as sweet it has become without his in-depth knowledge. These days I am delighted by the throttle improvements.

S-Prihadi

Since I am automatic tranny stupid...............
When I read the technical manual of 722.9, I wonder what BRAKE CLUTCH do ?
They are called BRAKE...as in to stop something/braking.

I know the K1 to K3 are power clutch-es to deliver power .






But when I read about planetary gear, I realized how damn smart the person who made this awesome 3-in-1 gear-set.
This gear set can do many things...wow, depending which one we lock ( hence BRAKE CLUTCH required ) and which want we want to move (K-s Clutch required).
Watch below :


Read some....
This one also explains : https://eng.kaps.cz/understanding-ho...-gear-sets-961

So, that is why BRAKE CLUTCH is required, to stop certain gears in order to make the gear set behave the way we want it to be.
That is my simplest explanation

Imagine a disc brake, the brake pad is the clutch material, the friction material...which we use our foot "actuation" is the input, the hydraulic brake fluid as thrust/pressure delivery liquid and the brake
booster boost our foot power. We modulate the brake with practice to produce the best smoothest braking effect in traffic jam, or in oldie non-ABS days, we modulate our foot like a solenoid to
bite maximum before brake rotor lock-up. That is what the BRAKE CLUTCH duty would be for smooth gear change, I guess.

Comes the K-s clutch pack. In manual tranny analogy, this is again our foot this time modulating friction and slip, along with the accelerator pedal, to deliver friction to create movement in the
smoothest possible fashion. I have to admit, regardless the hate I have for my Ford Fiesta PowerSH-IT automated manual dual dry clutch tranny poor reliability and comfort,
its first gear engagement and clutch release from zero stop to snail movement at under 800 RPM for an engine so small 1.6 liter and so low torque, is a mechanical feat very few trained
manual tranny user can match.

All of these beautiful mechanical orchestra is fluid driven... the tranny ATF fluid.
The fluid navigating within the maze wormhole of the valve body, in and out of solenoids, in and out of valves, thru small plastic and steel *****, thru small nylon check valve and towards the
piston which moves which every Brake Clutch -es or K-s Clutch. Holy cow..... what an engineering genius. Some history on AT tranny: https://www.caranddriver.com/researc...automatic-car/

The hydraulics I do on yachts are simple one, send it to a few hydraulic rams of steering system or crane/davits or bow/stern thrusters via solenoids, that is it. No pressure or friction balancing required.
Its OPEN and CLOSE only fluid flow... end of story. Yet we maintain cleanliness of the fluid with extreme care. There is no clutch wear particles to worry for me, mine is stand alone powered by
electric motor with its own fluid reservoir and spin-on filter and not a PTO version from main engine or its transmission.

All being explained : It all leads to ......drum roll ...........FLUID CLEANLINESS AND ITS STATE OF HEALTH, as the only component we can maintain/touch/mess-with.

=========================


Stingy Mercedes.
Just because my engine M276 3.0 TT has higher torque than M276 3.5 NA , I get one extra clutch. Our Tranny model number is different too.
I do not know the 100% difference yet, only some.

Look at the models of 722.9..... damn, so many !!!!














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Our torque converter is different too.



CLUTCH. Sorry I do not know this is which one.



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I wonder if say we install a higher torque auto tranny unit on a lesser torque car, will the tranny smoothness and driveability be the same, while surviving longer ?

On yachts I will choose a gearbox/tranny 1 or 2 model higher in its torque/HP rating when the duty is for Live On Board dive travel yacht which per year does 2,000 to 3,000 hours,
compared to pleasuren yacht which at best does only 500-1,000 hours for the most hardcore sportfishing yachts. No issue on comfort , as it is only forward or reverse, single gear ratio tranny.

....