722.9 Solenoid/Regulating Valve service
Thread Starter
Newbie
Joined: Aug 2025
Posts: 8
Likes: 1
From: Tasmania, Australia
CLS400 (218.365)
722.9 Solenoid/Regulating Valve service
Hi all,
I'm preparing to service the regulating solenoids on my 722.904 transmission in the near future. Now, I don't have access to Xentry/MB Star but I do have access to a friendly shop that can prompt a TCU adaptation for me, after I do the service. I presume that is sufficient after this work. Can anyone here please confirm that I won't require Xentry/MB Star for anything else, except this adaptation, if I take the valve body off the transmission to remove the solenoids for service?
I intend to remove the valve body, clean the solenoids including their mesh screens, clean the other mesh filter which is on the valve body/nearby, of which the name I can't recall now, replace the solenoid o-rings, and put it all back together. I am comfortable with the procedure, but and just hesitant about the software/Xentry work I will have to do afterward.
And yes, my process of diagnosis and a reasonable understanding of automatic transmissions has led me to this one thing as the cause of a few problems.
Thanks for your input.
Warm regards,
Rohan.
I'm preparing to service the regulating solenoids on my 722.904 transmission in the near future. Now, I don't have access to Xentry/MB Star but I do have access to a friendly shop that can prompt a TCU adaptation for me, after I do the service. I presume that is sufficient after this work. Can anyone here please confirm that I won't require Xentry/MB Star for anything else, except this adaptation, if I take the valve body off the transmission to remove the solenoids for service?
I intend to remove the valve body, clean the solenoids including their mesh screens, clean the other mesh filter which is on the valve body/nearby, of which the name I can't recall now, replace the solenoid o-rings, and put it all back together. I am comfortable with the procedure, but and just hesitant about the software/Xentry work I will have to do afterward.
And yes, my process of diagnosis and a reasonable understanding of automatic transmissions has led me to this one thing as the cause of a few problems.
Thanks for your input.
Warm regards,
Rohan.
Out Of Control!!
Joined: Apr 2019
Posts: 12,058
Likes: 6,848
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
Hi all,
I'm preparing to service the regulating solenoids on my 722.904 transmission in the near future. Now, I don't have access to Xentry/MB Star but I do have access to a friendly shop that can prompt a TCU adaptation for me, after I do the service. I presume that is sufficient after this work. Can anyone here please confirm that I won't require Xentry/MB Star for anything else, except this adaptation, if I take the valve body off the transmission to remove the solenoids for service?
I intend to remove the valve body, clean the solenoids including their mesh screens, clean the other mesh filter which is on the valve body/nearby, of which the name I can't recall now, replace the solenoid o-rings, and put it all back together. I am comfortable with the procedure, but and just hesitant about the software/Xentry work I will have to do afterward.
And yes, my process of diagnosis and a reasonable understanding of automatic transmissions has led me to this one thing as the cause of a few problems.
Thanks for your input.
Warm regards,
Rohan.
I'm preparing to service the regulating solenoids on my 722.904 transmission in the near future. Now, I don't have access to Xentry/MB Star but I do have access to a friendly shop that can prompt a TCU adaptation for me, after I do the service. I presume that is sufficient after this work. Can anyone here please confirm that I won't require Xentry/MB Star for anything else, except this adaptation, if I take the valve body off the transmission to remove the solenoids for service?
I intend to remove the valve body, clean the solenoids including their mesh screens, clean the other mesh filter which is on the valve body/nearby, of which the name I can't recall now, replace the solenoid o-rings, and put it all back together. I am comfortable with the procedure, but and just hesitant about the software/Xentry work I will have to do afterward.
And yes, my process of diagnosis and a reasonable understanding of automatic transmissions has led me to this one thing as the cause of a few problems.
Thanks for your input.
Warm regards,
Rohan.
What is it you are trying to fix?
What symptoms?
How did it get that way?
Can you use Xentry to diagnose BEFORE cleaning valves screens ??
Thread Starter
Newbie
Joined: Aug 2025
Posts: 8
Likes: 1
From: Tasmania, Australia
CLS400 (218.365)
@CaliBenzDriver Thanks. Rough, inconsistent shifts around the lower three gears... A mid-life service was missed in 2020/35,000km, and the oil was beginning to discolour when I checked it before it was changed 2025/93,000km. I suspect that this was enough bad treatment to allow debris to accumulate in the solenoids and spoil the o-rings.
The specific solenoids implicated, according to the gears I have trouble with, are the B1 Y3/8y5 and K1 Y3/8y2. I'm at the point of diagnosis where I want to just go in and test my theory.
But my question is, will I need access to Xentry for anything (other than prompting a TCU adaptation again) if I continue with this repair?
Thanks.
The specific solenoids implicated, according to the gears I have trouble with, are the B1 Y3/8y5 and K1 Y3/8y2. I'm at the point of diagnosis where I want to just go in and test my theory.
But my question is, will I need access to Xentry for anything (other than prompting a TCU adaptation again) if I continue with this repair?
Thanks.
Out Of Control!!
Joined: Apr 2019
Posts: 12,058
Likes: 6,848
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
low shifts performance
@CaliBenzDriver Thanks. Rough, inconsistent shifts around the lower three gears... A mid-life service was missed in 2020/35,000km, and the oil was beginning to discolour when I checked it before it was changed 2025/93,000km. I suspect that this was enough bad treatment to allow debris to accumulate in the solenoids and spoil the o-rings.
The specific solenoids implicated, according to the gears I have trouble with, are the B1 Y3/8y5 and K1 Y3/8y2. I'm at the point of diagnosis where I want to just go in and test my theory.
But my question is, will I need access to Xentry for anything (other than prompting a TCU adaptation again) if I continue with this repair?
Thanks.
The specific solenoids implicated, according to the gears I have trouble with, are the B1 Y3/8y5 and K1 Y3/8y2. I'm at the point of diagnosis where I want to just go in and test my theory.
But my question is, will I need access to Xentry for anything (other than prompting a TCU adaptation again) if I continue with this repair?
Thanks.
You want to go in a low milage 722.9 to replace solenoids to gain fresh O-rings because of poor low gears shifts...
Did you get any active TCU faults ?
Bad O-rings really are on the clutch pistons where shift frictions produce heat...
I have a more practical take on poor low gear shifts (2,3,4)... being caused by the engine THROTTLE not caused by poor TCU work.
Do you find your tranny always driving in the wrong gear selection... like 4th at 20mph or 5th at 30mph always having to manually intervene with gear selection ??
Overall response feels delayed and really heavy until rev's are up above 2500 to 3000R. That is common but not normal.
> Snappy vs. slippery...
Once engine setup is delt with, tranny automatically learns to performs snappy matched Rpm shifts all the way down to 2nd gear (... just not overnight!).
It learns appropriate gear selections, shifted near 2000R.
Matched rpm requires precise throttle else tranny is stuck with slow slippery shifts that work out hot frictions.
Pay attention to engine response to know how tranny is shifting your gears....
Smart tranny learns to adapt to the engine all by itself for seamless shifts.
Ppl report quick relief with getting TCU adaptations...
Last edited by CaliBenzDriver; May 10, 2026 at 04:32 PM.
Member
Joined: Mar 2026
Posts: 132
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The 722.9 (7G+) tranny is pretty robust and 93k km is still within the maintenance window. According to the Maintenance Manual (see page 18 of the attached), the tranny gets serviced every 77,500 miles (~125k km) or five years.
Pulling the valve body to clean the solenoids Is not impossible if you have any mechanical skills, but you should be sure the problem is with the solenoids first. XENTRY does have a process to calibrate the valve body solenoids, so you might want to try that first. From what I understand, solenoids are matched to the valve body at the factory (whatever that means) and do not have replaceable parts. But, whatever you do, make sure to properly tag each one so you know where it goes back. Put each on in a baggie and mark its location.
Pulling the valve body to clean the solenoids Is not impossible if you have any mechanical skills, but you should be sure the problem is with the solenoids first. XENTRY does have a process to calibrate the valve body solenoids, so you might want to try that first. From what I understand, solenoids are matched to the valve body at the factory (whatever that means) and do not have replaceable parts. But, whatever you do, make sure to properly tag each one so you know where it goes back. Put each on in a baggie and mark its location.
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