I purchased a new 2026 GLS 580 in February (just came off the truck with 5 miles on it) and it is completely undriveable in Comfort mode due to extremely harsh downshifts that shake/jolt the whole car. It happens at low to moderate speeds. If the car wasn’t brand new you would think it needed a new transmission. Today, with only 3,400 miles, the check engine light came on as well.
This is just a few of the many issues I’ve encountered so far. Anyone else experiencing this?

 

There is a software patch for that. It fixed ours.

Reb

 

MB has inherent corporate genetic defects in its ability to design and produce transmissions. The OP documents this. Old news since the 5G.

Too bad for owners of the S-Class of SUVs which are one year old to experience this.

MB should have long ago shuttered and abandoned its transmission activities and let the competent professionals at ZF and Aisin do the job. Graziano, Tremec and Cosworth can do one-offs for the GT platform.

Porsche and BMW discovered this secret years ago. MB with their heads in the sand can’t hear the banter at the water cooler.

 

Just another common problem on the one-sixty-lemon platform going on 7 years now. Take it to the dealership they have several fixes available.

 

I had debris in an accumulator of my 164 tranny. Fixed at 1,000 miles and it was the only problem the car had before I traded at 96,000 miles.
Total of about 400,000 miles on Benz transmissions, one shifting problem.
I particularly enjoy my 9spd Speedshift transmission at the track, where it maximizes my up and downshift points, rev-matches, and does not overheat, even with 105 degree ambient. My Cayenne wasn't that great, although it was a 2015 (ZF).

I DID have a issues with my McIntosh Preamp and my Parasound Amp, both excellent manufacturers. And a Stihl chainsaw. All fixed, I enjoy them a lot. Point being - a singular failure isn't an indication of Head In Sand.

It does provide a weak bit of fodder for Keyboard Warriors, though. It's our Internet Life these days.
Which is to say, I disagree.

 

Took it to the dealer yesterday. It needs a new valve body. They said that will fix the transmission issue. Not sure how a car with 3,500 miles can have that happen. Pretty disappointing.

 

Probably Debris, not wear.
I had such in a 2010 ML. Nothing recurred for the 95k miles of ownership.

 

Good that action is being taken and that it won’t cost you anything.

Entirely normal for MB, the best of nothing, sadly. Clearly quality control and reliability are nothing special on the S-Class of SUVs.

 

These things do happen. I had huge repairs done to both my Lexus LS460s within 5k miles. My 2015 had a bad head unit that with 400 miles on it had to have the whole dash torn out, and my 2017 had a bad brake actuator that had to be replaced with 5,000 miles on it.

I wouldn't overthink it, let them fix it and enjoy the car.

 

Good news.. and thanks for posting the solution. I had similar symptoms with my Lincoln Navigator, just on day-2 of ownership. Valve body was also the solution. My GLS is smooth but it has the inline-6 which to me is the only drivetrain from the modern era that couples nicely with the clunky crappy Mbenz transmission.

Agreed especially for the 1st one... but will emphasize again how the inline-6 can absorb some of these clunky shifts and meets magically (better but not ideal) with the crappy 9G. Every other V8 mbenz drivetrain I tested drove like crap and unfortunately most mbenz owners won't even realize they live 10-15 years in the past until they experience a ZF transmission by others. I do feel though that the inline-6 drivetrain kidna solves 80% of the crappy 9G transmission. I can bet that 99% of the vehicles on the road with the larger drivetrains have issues but people are just assuming this is normal... Nope.. in the 2020 era, cars of this caliber should just just as if they are EVs.. smooth non-existing shifts (yes it's been possible since mid 2010s with ZF transmissions. Also.. sensation of shifts in early 2020 ZFs in proper luxury cars like Alpina does not really exist at all.. can't even feel shifts if u try under normal driving conditions).. they shift and u would not even know it did. This should be the norm. I'd have felt very stupid to pay 3 digits for a car with clunky drivetrain. @Streamliner for example did the right thing and made them pay for that 2 times. Wish there are more people like him who wouldn't settle for nothing but perfect experience, at least we would not have seen mbenz dragging these 9G crappy transmissions for almost 2 decades now. It's foolish to even think these things are normal in a top lux german car.

 

They did that to my 2020 S560 which had a very harsh 3-2 downshift. It didn’t help. Then they “say” they replaced the entire transmission—which I don’t believe—and if anything, the problem got worse. Living in California, where MB knows what will happen due to the very consumer friendly Lemon Laws, the car was bought back.

I then had a new 2022 S580 which had the sloppiest shifting transmission of any car I can ever remember driving and that one was bought back, but for numerous other reasons.

Needing a car to drive, I bought a CPO 2020 S560 with 8,800 miles on it. The car was just like brand new, but after about six months, that car also developed the very harsh 3-2 downshift and they bought that one back.

That’s THREE 2020-2022 S Class sedans bought back in a row. I now drive a BMW I7 electric and whenever I drive an ICE vehicle, with all the thousands of machinery parts constantly moving and making noise, I just can’t wait to get back in my EV. If and when MB makes a REAL S Class EV, I look forward to giving such a car significant consideration.

 

BMW tunes the ZF8HP the best in the industry. VAG does a poor job with the same transmission.

The 8HP is like a Steinway D-274 piano. Unquestionably top in the world.

BMW plays the 8HP as a virtuoso plays the Steinway. VAG pounds on the horse teeth like Larry, Curly and Moe.

The 9G is like a Casio PX-S1100. An unelegant instrument played by someone (MB) who doesn't know they aren't a very good pianist.

 

You need to drive an AMG version. It's better than my Macan DSG.

 

I just did this weekend; primarily in an effort to test the different upgraded suspension setups on both the 580s and AMG. My dealer called me more than 2 weeks ago that he has what am looking for. I haven’t posted about it yet but will do soon. As for transmission, nope, not even close to ZF. 9G is 9G. Not sure about Macan but ZF in bmws is world class. 9G, as Chassis said, I don’t need to add more. AMG variant made no difference and in fact felt even harsher when shifting than my 450.

 

No question MB would be better off with the ZF 8 Speed.

 

The ZF in the Cayenne around 2019, 2020 wasn't great either. Harsh shifting in 2nd and 3rd gears. Plenty of owners complained about clunk or lurch when coming to a stop on Rennlist and Reddit.

 

My BMW i5 , granted not a 7 series is the biggest piece of crap I have ever owned. I lost count how many times I woke up to find that it didn't charge overnight and the car was non usable for hours. Their CarPlay connection is the worst, a virtual crap shoot if it connect. Sometimes it connects great as I am approaching the car, I stop in a store and no connection. BMW's response ...unpair your iPhone and repair it, reboot the car, reboot your iPhone. The system is terrible. I have less than a year to go and can't wait for it to be over. And I have 3 consecutive, Tesla Model S, so I think I am well versed in EV's. The only reason I went with this was because my son was getting his license and I would not let him drive a Plaid as his first car. They also put the worst tires on it, that barely lasted 12000 miles. BMW thinks anything they make is a high performance vehicle, the i5 is not. What drew me to it was the style and the fact that it does look like MB version of an EV. I also love the quiet of an EV.

 

the entire drivetrain tuning of the Cayenne was way too rough for me. Not a fan of how Porsche tuned it.

 

This is my point, there isn't any one place to go where you are guaranteed not to have issues.

 

I understand that issues can arise, after all they are mechanical and things happen, but it is how the company responds that matters. BMW, at least for me **** the bed. I really believe if it was an ice vehicle they would have swapped it, they absolutely refused and a Lemon Law attorney said they will make it difficult for me to succeed and in all likely hood would take years to get a decision. He wasn't willing to take them on, I think they all want slam dunk cases, and BMW is very creative in how they word the complaints and their responses. So far so good with my GLS, I would never have paid close to the sticker that it is spec'd at and we satisfied with my particular vehicle.

 

That hasn't been my experience.
Be aware, though, that the transmission remembers your most recent driving habits. So if you spent a few blocks checking the performance, the transmission will apply that driving strategy for quite a while and it will be in a kind of Sport+ mode.
If you are in Comfort but stab the gas pedal, it essentially overrides the C setting and becomes Sport+ for quite a while, raising shift points with harsher shifts. Pedal velocity and position both effect that adaptation.
So if you want to compare a soft shift mode, you have to let the car "forget" your aggressive behavior.

The Macan has a DSG Dual Clutch transmission, which was smoother than my Cayenne, but my 9G Speedshift is smoother than either of those. In normal driving.

Test drives are hard for comparisons. For ride and handling, I actually carry a tire gauge to check tire pressures. (Which also gives insight into the care that the Dealer put into the PDI - a glimpse into their Service Department.) My last X5 test drive exposed some really sloppy handling, and after correcting tire pressure it improved, but not to the point of being "crisp." Front washout.

 

Wow...yeah that is frustrating.

 

It turns out the valve body is on backorder, with no ETA.
This tells me it’s probably become a substantial problem for Mercedes if they can’t keep up with valve body replacements.

On a side-note, regarding the AMG, both the sales rep and my service advisor (who has taken care of me for the last six years with my previous S550 & previous GLS 450) said to stay away from the GLS AMG. It’s quite an indictment on the AMG if they both steered me away from it. Their opinion is only for the GLS, and not the S class or SL version of the AMG, which they think are pretty awesome.

 

I wouldn't assume that, we haven't seen a lot of talk about it here.

I would also take what your salesman and service guy say with a grain of salt. In fact the S Class AMG which is the PHEV has considerable problems while I haven't really seen anything posted here about the GLS AMG. A lot of salespeople like to talk without really worrying about what they are saying...

 

The current S and especially the current SL have—or at least have HAD—their own share of major issues. I believe the W223 S Class was pretty much cured by the 2024 or 2025 models, but the R232 SL issues are near “legendary” and to the point where the factory appears to not be taking any custom orders currently, trying to work through the colossal number of “buy-back” cars on the market right now.