2015 550 Coupe rough downshift
Thread Starter
Junior Member
Joined: May 2023
Posts: 40
Likes: 2
From: Maryland
2015 S550 Coupe
2015 550 Coupe rough downshift
New to me 550 Coupe. No issues for a week of driving in Maryland, placed drive train in Sport for a few miles then back to Eco. Next day noticed rough downshift 4-3-2 when coasting to stop light, Light brake. No brake was even worse. Put back to Sport then to Eco...better for a while then rough again?? Intermittent not Constant
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Joined: Jul 2007
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From: Santa Barbara, CA
S550C4, Porsche Cayenne
New to me 550 Coupe. No issues for a week of driving in Maryland, placed drive train in Sport for a few miles then back to Eco. Next day noticed rough downshift 4-3-2 when coasting to stop light, Light brake. No brake was even worse. Put back to Sport then to Eco...better for a while then rough again?? Intermittent not Constant
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From: Charlotte, NC
Had: 1987 300TD, Had: 2004 C230 Sport Sedan, Have: 2014 E350 Sport, Have: 2019 S450
Some can say it’s placebo effect, but most harsh downshifts stopped about the time I unplugged the oil pump solenoid. Do so at your own risk, but that is my observation
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From: Phoenix
222 S-65
OP fresh transmission fluid is always good for them. First service due at 60,000 and every 30K thereafter. Begs the question.... why not every 30,000 to start with! Answer is obvious... attempt at keeping maintenance costs down while under warranty. They know it will happily live to 60K on original oil... but it will be overdue by then.
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From: NY & FL
MB’s of all kinds.
How many miles ? Might be time for a transmission oil change. I do mine every 30k. It just makes sense. FCP Euro sells a kit with everything. These 7 speeds like that and it does them well.
Last edited by C280 Sport; Jan 24, 2026 at 01:26 AM.
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MBWorld Fanatic!
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From: Phoenix
222 S-65
Benz Ninja can flash software that changes how the transmission behaves. For the better. Among other things. Oh look! His banner ad is at the top of the page.
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From: Phoenix
222 S-65
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2013 W221 S550 2016 C217 S550
OP. Do you have service records? Was your transmission fluid ever changed? Need to use the right fluid too. Change it? Needs to be done probably? Also, check for oil leaks at the front of the engine.Not transmission related, just m278..... stuff
Last edited by red996; Jan 25, 2026 at 02:11 PM.
Thread Starter
Junior Member
Joined: May 2023
Posts: 40
Likes: 2
From: Maryland
2015 S550 Coupe
Took my baby in today, shop said there was a recall on the exact problem I described, rough shift from 5th to 4th. Checked software and update had been performed. They are changing fluid and filter and (reseting software)?
Stay Tuned
Stay Tuned
Super Member
Joined: Jul 2007
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From: Santa Barbara, CA
S550C4, Porsche Cayenne
Doo you have any identifying info about the recall - name or number? - that we could reference with our dealers?
Thread Starter
Junior Member
Joined: May 2023
Posts: 40
Likes: 2
From: Maryland
2015 S550 Coupe
I haven't picked the car up yet, service manager emailed this to me.
Bulletin provided to me by Autowerkes Belair Maryland
https://static.nhtsa.gov/odi/tsbs/20...76661-9999.pdf
Bulletin provided to me by Autowerkes Belair Maryland
https://static.nhtsa.gov/odi/tsbs/20...76661-9999.pdf
Super Member
Joined: Jul 2007
Posts: 743
Likes: 228
From: Santa Barbara, CA
S550C4, Porsche Cayenne
I haven't picked the car up yet, service manager emailed this to me.
Bulletin provided to me by Autowerkes Belair Maryland
https://static.nhtsa.gov/odi/tsbs/20...76661-9999.pdf
Bulletin provided to me by Autowerkes Belair Maryland
https://static.nhtsa.gov/odi/tsbs/20...76661-9999.pdf
Thread Starter
Junior Member
Joined: May 2023
Posts: 40
Likes: 2
From: Maryland
2015 S550 Coupe
Picked up the car this morning, it's 40° here in Maryland and the rough downshift is still there. They did a full transmission service, new fluid, filter, etc. $1000 Went back to the shop and talked with the service manager, he said it could take a couple hundred miles for the updates and new adaptations to fully take affect. On the plus side, it updated the Comand center with new graphics, and the pneumatic seat functions have returned.
Last edited by Miwettig; Feb 21, 2026 at 08:38 AM.
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From: Half Moon Bay, CA
2016 S550e, 2005 Nissan Xterra 4x4, 1984 300ZX
Really new graphics? I had same issues and software update and followed by the tanny service got much better but still has some issue I have just learnd to live with it. Before that while under CPO warranty I literaly though someone had rear ended me it was so brutal, it got way better but still not as smooth as I would like.
Thread Starter
Junior Member
Joined: May 2023
Posts: 40
Likes: 2
From: Maryland
2015 S550 Coupe
My Bad... The graphics haven't changed. I believe when I picked it up and was the first to start it after the update… I guess… There was a spinning globe in the command display that I never saw before, but I have not seen it again.
Rough downshift is still there when temp is below 45°. Service manager said to give it a couple hundred miles for the system to learn the new updates. Something else I noticed that I didn't notice before is that it skip shifts when breaking. 6–4–2. It may have done it before but I didn't notice because I wasn't looking at the display.
Rough downshift is still there when temp is below 45°. Service manager said to give it a couple hundred miles for the system to learn the new updates. Something else I noticed that I didn't notice before is that it skip shifts when breaking. 6–4–2. It may have done it before but I didn't notice because I wasn't looking at the display.
Last edited by Miwettig; Feb 25, 2026 at 07:54 AM.
