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I have been one of the only posters to make aware of the solenoid O-ring problem (many times I have called them shift spools)
From a great article
“As usual, the simplest things can lead to major problems in the 722.9. The majority of the failures we’ve run into are caused by the O-rings on the tips of the solenoids deteriorating, leaking fluid, and not properly stroking valves (figure 1). We’ve seen the O-rings cut, some missing, and the clutch they operate usually burns.”
I would highly advise for the DIY when changing transmission fluid to drop the valve body and pull all 8 solenoids out .. clean the screens and inspect the Orings. I have done it to 3 transmissions and all of them had Orings ripped, cracked and a few missing that caused a bunch of problems.Take a few minutes and read the article . In the picture below is the source I USED AND THE SIZES I DETERMINED. You might want to size them and pick your own source. My MB trannys did work fine after my tear down and refit with O-rings. I always keep a complete set in my supplies. The picture with the yellow glove is one out of my 2008 GL550.
The original article can be found at
https://gearsmagazine.com/magazine/common-mercedes-722-9-problems/#
Last edited by vesiadog; Jun 18, 2024 at 07:48 PM.
Reason: wording
Problem is common to a lot of transmissions of this vintage, but it is perfectly sensible to do so during the service. I bet mine are rock hard and will come out in chunks.
Problem is common to a lot of transmissions of this vintage, but it is perfectly sensible to do so during the service. I bet mine are rock hard and will come out in chunks.
Way more common on the 7 speed than the MB 5 speed that is even older. I have worked on many 5 speeds and have not seen many bad O-rings on the solenoids.
How hard is taking the valve body out compare to 722.6 5 speed? I have taken the 5 speed out a few times but never on the 722.9.
Any tips and tricks greatly appreciated.
How hard is taking the valve body out compare to 722.6 5 speed? I have taken the 5 speed out a few times but never on the 722.9.
Any tips and tricks greatly appreciated.
Pretty much the same.. pan, filter and find all the bolts to remove… biggest caution is the electrical connector .. very careful handling NOT to break the Electrical connector away from the assembly. I would say in general once you have gone over 100k miles it is time to drop the valve body assembly.
The company I posted the picture of where I bought the O-rings from … the owner was a Transmission rebuilder before this new O-ring business. He felt that Mercedes has used some lower quality O-rings and they were not holding up to the various temps.
No real proof just an opinion.
My biggest reason for posting the article was for PREVENTION…Once the transmission starts to act up with hard shifting etc…,I would go right to the valve body … clean, inspect and replace. Of course Mercedes dealers do not have the O-rings you have to replace the Solenoid (x8) at over $100 a piece . I think with shipping and the minimum buy it will cost around $20-25 for the O-rings.
Part numbers for the solenoids
Blue cap 220-277-09-98
Black cap 220-277-10-98
Used sets are all over ebay but it took me a while to come up with the proper fitting O-rings… had to order a few sizes at first.
I did find this kit today… Never used this kit but definitely a reliable company .
https://cobratransmission.com/722.9-Solenoid-Oring-Kit Mercedes Benz 722.9 Automatic Transmission Solenoid O-Ring Kit. (Contains 10 x IPN6-56220 And 10 x IPN6-58323)
$12.99
Another source states the lower O-ring MB part number is 011-997-1448-64
I have them measured at 8.5mm-1.5mm
I read another post claiming 8.0-1.5???
Last edited by vesiadog; Jun 19, 2024 at 01:25 PM.
Reason: wording
Bill, thank you again, this is super valuable info, greatly appreciated.
In my W210 days, had a hard shift issue popped up out of nowhere, it was only 1 to 2 or 2-1, took the valve body down, swapped the solenoids to 4 to 5 and sure enough, 1 to 2 turned to butter but this time 4-5 was a bit noticeable, wasn`t as bad as when it was on 1-2 but still noticeable.
Next time I got a new solenoid and the issue was gone.
Missed the 5 speed so much, such an easy transmission to work on, drain and fill is so easy even my 12 year old can do it. No need for programming the conductor plate, cheap parts, easy work, that tranny was shifting like the first day at 245K.
Bill, thank you again, this is super valuable info, greatly appreciated.
In my W210 days, had a hard shift issue popped up out of nowhere, it was only 1 to 2 or 2-1, took the valve body down, swapped the solenoids to 4 to 5 and sure enough, 1 to 2 turned to butter but this time 4-5 was a bit noticeable, wasn`t as bad as when it was on 1-2 but still noticeable.
Next time I got a new solenoid and the issue was gone.
Missed the 5 speed so much, such an easy transmission to work on, drain and fill is so easy even my 12 year old can do it. No need for programming the conductor plate, cheap parts, easy work, that tranny was shifting like the first day at 245K.
5 speed was a great simple tranny BUT if neglected without fluid changes would turn into trouble also.
Once I dug into a few 7 speeds and fix a couple with the O-rings I wanted to share the info. Found that article last night. I wouldn’t tear into one for no reason but after 100k I definitely would drop the valve body.. there are enough videos out there to also show you how to clean out certain ports etc. I use a simple carb or brake cleaner spray.
My recent purchase of a 2011 GL550 with 75k miles was a tough decision not to drop the valve body but it absolutely shifts perfect so I drained the TC , filter and 9.5 Qrts BUT next change around 105-100k miles it will be dropped and all new O-rings will be put in.
Last edited by vesiadog; Jun 19, 2024 at 07:25 PM.
All this actually proves my theory with the 722.9, I do 20K mile fluid changes with just the pan drain plug( without tackling the green plastic in the pan, just unscrew the plug and drain whatever comes out, usually close to a liter) and Torque convertor(2 liters), that gives me total about 2.5 to 3 liters fluid to refresh.
And at 40K I do a full change including gasket, filter, torque convertor etc.
If I happen to miss my 20K service then I`m doing a full service at 30K.
I know some of you will criticize me for that but I put a lot of miles, long trips in extreme temperatures, have little kids. Can`t imagine getting stuck middle of nowhere in CO, Utah or Idaho when its 105 out or 5 degrees.
All this actually proves my theory with the 722.9, I do 20K mile fluid changes with just the pan drain plug( without tackling the green plastic in the pan, just unscrew the plug and drain whatever comes out, usually close to a liter) and Torque convertor(2 liters), that gives me total about 2.5 to 3 liters fluid to refresh.
And at 40K I do a full change including gasket, filter, torque convertor etc.
If I happen to miss my 20K service then I`m doing a full service at 30K.
I know some of you will criticize me for that but I put a lot of miles, long trips in extreme temperatures, have little kids. Can`t imagine getting stuck middle of nowhere in CO, Utah or Idaho when its 105 out or 5 degrees.
For how much little time that takes it all makes sense to me. Refreshing 2.5 to 3 Liters and then a complete change… Actually well spent money in my book. What brand tranny fluid do you use?
A friend of mine who I have mentioned before that designs and manufactures oils actually has a transmission package .. a small 16oz bottle with a lot of updating chemicals to help a tranny along!!
Last edited by vesiadog; Jun 20, 2024 at 01:31 PM.
Reason: wording
I use Fuchs Titan 7134, a while ago had locked a pretty good deal on that, stocked 12 of 5 qt jugs. I also have a 2011 W212 with same tranny, used almost 5 of the 12 jugs between the GL and E class.
The stock I have would probably last me another few years.
You are absolutely right about how little time it takes, actually jacking up and securing the vehicle takes most of the time.
I got a rebuilt transmission a few years back. I am inclined to ask the shop about the o-rings on the solenoids in the valve body. Will report back if I get a reply.
I got a rebuilt transmission a few years back. I am inclined to ask the shop about the o-rings on the solenoids in the valve body. Will report back if I get a reply.
We will be waiting for your insight from the shop!!!
The transmission rebuilder recognizes the problem; at least, they say they replace the o-rings with good ones. So yeah, if you have an original transmission, probably wise to check and replace. Good to know.
The transmission rebuilder recognizes the problem; at least, they say they replace the o-rings with good ones. So yeah, if you have an original transmission, probably wise to check and replace. Good to know.
So what you are saying is the articles and experienced posters who have dealt with the O-ring problems in the past are correctly warning ???? Thank you Eric for checking out my post ! 😂
Fantastic. Glad I found your post.
Is that size an inside diameter?
If so I'll ask for I.D. 8.5 mm x 1.5mm fleuroelastomer - branded FKM or Viton.
I'll try and find some locally, otherwise it's like $50 to $100 postage from Cobra to NZ.
I can't find theoringstore.com on the web. Maybe they've gone out of business.
Also curious how the cross-over pipe looked? I see some places selling those. Which made wonder - do those fail? Looks like a white plastic pipe with 2 o-rings and some sort of grommet in the middle - guessing it supplies oil to the valve body.
New Zealand. Yeah, that was the problem. Used a VPN and theoringstore showed up fine. So 8.5mm is an inside diameter. They have a very good range. 8.5mm seems to be a bit of an odd size. But I'll track some down.
Cross Section "CS" X Inside Diameter "ID"1.5mm X 8.5mm V75 Fluorocarbon FKM O-Rings 75/80 Durometer Black (JIS S9-V75)
Which part of New Zealand are you in? I can access the oringstore fine here in Australia.
Originally Posted by tommokw
Fantastic. Glad I found your post.
Is that size an inside diameter?
If so I'll ask for I.D. 8.5 mm x 1.5mm fleuroelastomer - branded FKM or Viton.
I'll try and find some locally, otherwise it's like $50 to $100 postage from Cobra to NZ.
I can't find theoringstore.com on the web. Maybe they've gone out of business.
Also curious how the cross-over pipe looked? I see some places selling those. Which made wonder - do those fail? Looks like a white plastic pipe with 2 o-rings and some sort of grommet in the middle - guessing it supplies oil to the valve body.
Which part of New Zealand are you in? I can access the oringstore fine here in Australia.
Waikato. I don't know how those restrictions work. Guessing the store nominates which countries it allows. Or maybe we got grouped with Norfolk Island on the list of exporters that can't be trusted 🫢
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