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Hello! My MB have been acting up recently and I think the problem is the automatic gearbox but I'm not really sure. The problem is that when I'm doing a medium to hard acceleration from 1st or 2nd gear, it feels like the tires are slipping (dry asphalt - no chanse): the RPM increases but not the acceleration. After a second I think the ECU catches up and limits engine power, and the car does a jerk. If I keep the acceleration a whine can be heard until I let go of the accelerator, kind of sounds like a "reverse gear whine", but not completely. I also noticed a new "whoo" sound when the gear changes kinda like a diverter/blow off valve. All the other gears work just fine, it's just 1st and 2nd.
My guess would be it's a problem with the gearbox, but I have no clue where to start. I've asked some shops if they can diagnose a Mercedes gearbox, but I've gotten no answer yet. Closest Mercedes dealer is about 1h away and wanted $200-$300 for a diagnosis. If there's a tool I can buy that can diagnose a MB gearbox I'd rather spend those money for a DIY.
Hello! My MB have been acting up recently and I think the problem is the automatic gearbox but I'm not really sure. The problem is that when I'm doing a medium to hard acceleration from 1st or 2nd gear, it feels like the tires are slipping (dry asphalt - no chanse): the RPM increases but not the acceleration. After a second I think the ECU catches up and limits engine power, and the car does a jerk. If I keep the acceleration a whine can be heard until I let go of the accelerator, kind of sounds like a "reverse gear whine", but not completely. I also noticed a new "whoo" sound when the gear changes kinda like a diverter/blow off valve. All the other gears work just fine, it's just 1st and 2nd.
My guess would be it's a problem with the gearbox, but I have no clue where to start. I've asked some shops if they can diagnose a Mercedes gearbox, but I've gotten no answer yet. Closest Mercedes dealer is about 1h away and wanted $200-$300 for a diagnosis. If there's a tool I can buy that can diagnose a MB gearbox I'd rather spend those money for a DIY.
To begin, to my understanding, on the 722.9 1-2 is a hard **** because the torque converter is "letting go" in a sense" . Have you serviced the transmission? The most common issue reported here has to do with the valve body. That's all I can think of off the bat.
To begin, to my understanding, on the 722.9 1-2 is a hard **** because the torque converter is "letting go" in a sense" . Have you serviced the transmission? The most common issue reported here has to do with the valve body. That's all I can think of off the bat.
The transmission was serviced 2 or 3 years ago, at a Mercedes shop. I've never been working with automatic gearboxes before, I suppose the valve body is something internal?
This guy gives a hilarious description of the issue including camera shakes
That sounds exactly like my problem! He says the turbine speed sensor requires a gearbox teardown to replace, but in a comment someone says it's fixed by replacing the the conductor plate. Sounds expensive either way
Are the conductor plate accessible from underside the gearbox? Or does it need to be drained and teared apart?
Here's a lnk to a guy in Jersey that seems pretty knowledgeable able the 722.9 Valvebody. Watch and listen maybe you'll have an epiphany https://www.youtube.com/watch?v=PCG4plcPC_8
Thank you! I did have a look at some gearbox teardown videos, and it looked fairly simple to remove the valve body and conduit plate, and also refill the oil. I just lack a car lift and a clean environment for a DIY. Laying on the literal dirt floor in my "garage" wouldn't seem to be optimal when working on a gearbox.
Sort of off topic, but does anyone know if I would be missing some features if I bought the iCarsoft CR MAX, Pro or Elite instead of the MBII or MBV2.0?
I think I would rather spent my money on a reader that can do every car than just a Mercedes one.
I went ahead and spent the extra to get the CR Plus I think and I'm glad I did. Buying just the MB one would've limited its usefulness quite a bit.
If you're in the Seattle area you could hook up mine and give it a look. I would recommend seeing if you can find someone in your area that has a MB Star system, though. That'll give you the absolute best look at what's going on.
I went ahead and spent the extra to get the CR Plus I think and I'm glad I did. Buying just the MB one would've limited its usefulness quite a bit.
If you're in the Seattle area you could hook up mine and give it a look. I would recommend seeing if you can find someone in your area that has a MB Star system, though. That'll give you the absolute best look at what's going on.
Thank you for the offer, but I'm located basically on the other side of the globe. Bought the iCarsoft CR Pro, waiting for it to be delivered this week. I saw a thread about using Xentry with some cheap adapter, I'll go that way if the iCarsoft doesn't provide all necessary information.
Well I got my iCarsoft today. Plugged it in, entered the gearbox module, scanned for codes and it showed.. No codes found!?
It could read every value and find codes from other modules. Not sure what to make of it? Can't believe there are no codes when it's such an obvious problem.
What should I try next? I'm thinking of trying to check if it's enough gearbox oil, but I doubt it would be such a simple solution.
Well I got my iCarsoft today. Plugged it in, entered the gearbox module, scanned for codes and it showed.. No codes found!?
It could read every value and find codes from other modules. Not sure what to make of it? Can't believe there are no codes when it's such an obvious problem.
What should I try next? I'm thinking of trying to check if it's enough gearbox oil, but I doubt it would be such a simple solution.
Always check the basics first once you hit a wall and before firing the parts cannon. Have you changed the transmission mount?
Still haven't found anywhere to check the oil level and under the car. I tried some logging with the iCarsoft but I really have no idea what I'm looking at or what to look for, so no luck yet.
But does anyone know if the 722.9 gearbox are completely electrically and hydraulically driven? No vacuum or anything else? Because I'm pondering what the whining sound could be, it sounds like it's coming from in front of the dashboard.
Before proceeding find someone who can pull codes using MB diagnostics (Xentry, SDS, etc.). Valve body/conductor plate is inside transmission. See attachments for oil change/fill.
2016 E350 4Matic wagon, 2019 Ford Expedition, 2019 Chevy Bolt EV
Originally Posted by Antisladd
Still haven't found anywhere to check the oil level and under the car. I tried some logging with the iCarsoft but I really have no idea what I'm looking at or what to look for, so no luck yet.
But does anyone know if the 722.9 gearbox are completely electrically and hydraulically driven? No vacuum or anything else? Because I'm pondering what the whining sound could be, it sounds like it's coming from in front of the dashboard.
722.9 transmission oil level is checked by opening the drain plug, pumping some more into it, and letting it drain out to the top of the tube thats around said plug
servicing your valbody is not so difficult
updating your transmission module and all other modules can be done for free lifetime with my service
You'll go nowhere with Icarsoft and other cheap tools like that
Ah sorry I was a bit unclear, I meant that I'm still at the stage looking for a physical place to do the work at. And/or someone knowledgeable around my area. I've only got a basic garage with a dirt floor, which I guess its not optimal when opening a gearbox.
Also, this has to be the first and only time I'm happy that the Check engine light has came on. It light up this morning when the gearbox acted up, and when I pulled codes i got P073000 ("There is an impermissible transmission ratio") and P073200 ("Gear 2 is unreasonable or the transmission is slipping"). Both however came up as Historic.
Last edited by Antisladd; Aug 7, 2022 at 04:49 PM.
Before proceeding find someone who can pull codes using MB diagnostics (Xentry, SDS, etc.). Valve body/conductor plate is inside transmission. See attachments for oil change/fill.
Thank you for the information, very useful!
Does the 'proper' softwares show codes the iCarsoft cannot find? Or is it just that it can access more information?
Originally Posted by Left Coast Geek
722.9 transmission oil level is checked by opening the drain plug, pumping some more into it, and letting it drain out to the top of the tube thats around said plug
(he's very meticulous about jacking the car up and putting it on stands so its perfectly level, this takes the first 3:50 of the video)
re: actuation, the control is entirely electronic, the internals are entirely hydraulic.
I'll have a look, thank you!
Gotcha, that rules out vacuum leak from the gearbox. Although it sounds like it comes from the back of the engine.
Originally Posted by BenzNinja
servicing your valbody is not so difficult
updating your transmission module and all other modules can be done for free lifetime with my service
You'll go nowhere with Icarsoft and other cheap tools like that
Could a software update solve problems like this? This feels more like a physical problem.
Update on the problem: finally a shop had time to have a look at it, and they found that problem are most likely caused because of low oil level in the gearbox caused by a busted o-ring at the transmission oil cooler. So hopefully it's just to change the oring and top up the gearbox. Right now we are waiting for the new orings.
However another problem arose, he told me that apparently the refill procedure for the gearbox in the 220 CDI are not the "open the plug and analyse the stream", but apparently it's that you're supposed to drain the oil completely and simply refill the correct amount. Which means my options are to either drain and reuse the old oil and just top it up before refill, or to drain and use new oil altogether. At $32 a litre it's quite an expensive oil.
But I'm curious, does anyone have any information about this "alternative" refill procedure? The only ones I've found are the one where you analyse if it's a stream or dripping from the refill hole at the bottom, not anything about pre-measure and just pump it in. I'm kinda confused as well as he told me the capacity is "about 6-7 litres", but from what I recall (actually checked the recipe) when I did a transmission service at Mercedes some years ago, it required 10 litres. Guess he could have took the value from the top of his mind without really checking first.
Edit: just clearing some things up, wrote the post in a hurry earlier.
Last edited by Antisladd; Aug 24, 2022 at 05:43 PM.
I did have a chat today again with the guy doing the work trying to get some details. He told me again that the specific gearbox in my car are simply filled with a specific amount of oil and not by using the overflow technique, as he "saw it on youtube". He even went to tell me that there was no overflow pipe and told me to buy a new oil pan with one fitted.
However everything I find on the web points to that there are indeed an overflow pipe and that's the only correct technique to refill the oil. I think he's basing his theory that there were oil flowing out when he opened the drain plug, but if I were to guess I would guess that he did not warm the gearbox up to 45 degrees C beforehand and/or did not have the engine running, which would explain the excess amount of oil. So right now I'm in a situation where I have to second guess the mechanic and might even have to convince him he's wrong to get my car properly fixed..
But, for the sake of it, could it be possible that the overflow pipe are damaged or have come loose? Or that there actually are some specific gearboxes that have no pipe? Right now I need every bit of argument that I can find.
2016 E350 4Matic wagon, 2019 Ford Expedition, 2019 Chevy Bolt EV
Originally Posted by Antisladd
Update on the problem: finally a shop had time to have a look at it, and they found that problem are most likely caused because of low oil level in the gearbox caused by a busted o-ring at the transmission oil cooler. So hopefully it's just to change the oring and top up the gearbox. Right now we are waiting for the new orings.
However another problem arose, he told me that apparently the refill procedure for the gearbox in the 220 CDI are not the "open the plug and analyse the stream", but apparently it's that you're supposed to drain the oil completely and simply refill the correct amount. Which means my options are to either drain and reuse the old oil and just top it up before refill, or to drain and use new oil altogether. At $32 a litre it's quite an expensive oil.
But I'm curious, does anyone have any information about this "alternative" refill procedure? The only ones I've found are the one where you analyse if it's a stream or dripping from the refill hole at the bottom, not anything about pre-measure and just pump it in. I'm kinda confused as well as he told me the capacity is "about 6-7 litres", but from what I recall (actually checked the recipe) when I did a transmission service at Mercedes some years ago, it required 10 litres. Guess he could have took the value from the top of his mind without really checking first.
Edit: just clearing some things up, wrote the post in a hurry earlier.
Some update on the issue again: somehow Mercedes sold me the wrong o-rings as they where to small. He changed the o-rings for some he thought looked the same and topped up the gearbox (the correct way). Apparently he had to fill it up 3 litres, which definitely would explain why it acted a bit funky. He took it for a test drive and the shifting problem seemed to be gone.
However when he inspected he found that it was still leaking and told me the transmission oil cooler would have to be replaced. I can't find any information about it on the internet, so it does not seems to be a very common problem.
Are there anything I should have in mind or worry about regarding the oil cooler leak? Could it be the pipes that are leaking?
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren
Slideshow: A one-of-one U.S.-spec Mercedes-Benz SLR McLaren Roadster became even rarer after a factory-backed transformation at McLaren's headquarters.
