Odd random bucking/jerking/kangarooing in 3rd gear
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Joined: Jun 2022
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2020 C63 Cabriolet
Odd random bucking/jerking/kangarooing in 3rd gear
Hi everyoneI have a stock 2020 C63 cabrio. 23k miles
Sometimes when accelerating very slowly going through gears 1-2-3, the car starts to hesitate to pick the next gear causing the rpm to drop and raise drop and raise a few time until it finally picks the 4th gear. It almost feels like the car doesn't know which gear to pick.
This has been more or less happening since I bought the car. Only happens when in 3rd gear, in S+, and when the car isn't cold. I've never noticed it happen with it's in Sport ESP
I know about the wet clutch problem, but this seems different as it only happens in 3rd gear and when going very slowly.
The dealer has been unable to reproduce it. I can barely reproduce it on demand. I can drive it for a week without it happening and all of a sudden it does it randomly, then I can reproduce it more consistently by driving really slow again from a full stop. But even then it's not consistent.
I've tried the reset TCU trick, and the dealer supposedly reset the TCU for me the last time it was in for service. But it comes back.
Does anyone have any idea what this could be?
BestHT
Sometimes when accelerating very slowly going through gears 1-2-3, the car starts to hesitate to pick the next gear causing the rpm to drop and raise drop and raise a few time until it finally picks the 4th gear. It almost feels like the car doesn't know which gear to pick.
This has been more or less happening since I bought the car. Only happens when in 3rd gear, in S+, and when the car isn't cold. I've never noticed it happen with it's in Sport ESP
I know about the wet clutch problem, but this seems different as it only happens in 3rd gear and when going very slowly.
The dealer has been unable to reproduce it. I can barely reproduce it on demand. I can drive it for a week without it happening and all of a sudden it does it randomly, then I can reproduce it more consistently by driving really slow again from a full stop. But even then it's not consistent.
I've tried the reset TCU trick, and the dealer supposedly reset the TCU for me the last time it was in for service. But it comes back.
Does anyone have any idea what this could be?
BestHT
Out Of Control!!
Joined: Nov 2018
Posts: 11,467
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From: San Francisco Bay Area
2019 C63CS
Have you ruled out your foot actually moving back and forward on the throttle pedal? That's the most common cause of bucking due to the direct connection between the engine and transmission, short gearing and very responsive throttle. Doesn't happen often, but at times I cause a bucking that way and the solution is to remove my foot from the throttle to settle everything and then get back on it.
Aside from that it seems that most people who have issues with the transmission are like you doing normal driving in S+ instead of C. I've long had this theory that the transmission doesn't really know how you want to drive if you put it in S+, but then not actually drive sporty/dynamic. Even the instructors at the AMG Driving Academy told us to use use S+ etc. only for fast and dynamic driving. Highway is fine, but don't use around town. I also don't actually drive in automatic mode when in S+ etc. other than in C, I shift manually, so my transmission only had to adapt to my normal moderate driving instead of finding a compromise between my normal and my sporty driving. I mostly toggle between C for around town, and I* for open road and highway driving and I have my Individual mode set up to put the transmission in M. To me that's the only way to really drive these cars outside of taking it easy in C around town or on long highway journeys. As opposed to the old 7 speed, C is actually responsive in the 9 speed partly due to the much shorter first 7 gears and always starting in 1st gear as opposed to the slurry 2nd gear start of the 7 speed, and the manual mode is also instant in the 9 speed whereas it was laggy in the 7 speed.
Aside from that it seems that most people who have issues with the transmission are like you doing normal driving in S+ instead of C. I've long had this theory that the transmission doesn't really know how you want to drive if you put it in S+, but then not actually drive sporty/dynamic. Even the instructors at the AMG Driving Academy told us to use use S+ etc. only for fast and dynamic driving. Highway is fine, but don't use around town. I also don't actually drive in automatic mode when in S+ etc. other than in C, I shift manually, so my transmission only had to adapt to my normal moderate driving instead of finding a compromise between my normal and my sporty driving. I mostly toggle between C for around town, and I* for open road and highway driving and I have my Individual mode set up to put the transmission in M. To me that's the only way to really drive these cars outside of taking it easy in C around town or on long highway journeys. As opposed to the old 7 speed, C is actually responsive in the 9 speed partly due to the much shorter first 7 gears and always starting in 1st gear as opposed to the slurry 2nd gear start of the 7 speed, and the manual mode is also instant in the 9 speed whereas it was laggy in the 7 speed.
Thread Starter
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Joined: Jun 2022
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2020 C63 Cabriolet
^ thank you for your response. No, it's definitely not the foot. I thought the same too at first. But it's so specific to the 3rd-to 4th gear change and certain speeds that I was able to rule that out.
I understand your argument. I might just be confusing the TCU. I normally drive in S+ auto all the time. But your are right: C can pick up speed just as well when pushed. I usually drive in a very spirited manner. When Im stopped at a light behind other cars that drive more sanely than me is when this issue creeps up from time to time 😂
I understand your argument. I might just be confusing the TCU. I normally drive in S+ auto all the time. But your are right: C can pick up speed just as well when pushed. I usually drive in a very spirited manner. When Im stopped at a light behind other cars that drive more sanely than me is when this issue creeps up from time to time 😂
Last edited by Doc2c; Aug 7, 2022 at 06:36 PM.
Out Of Control!!
Joined: Nov 2018
Posts: 11,467
Likes: 5,356
From: San Francisco Bay Area
2019 C63CS
I understand your argument. I might just be confusing the TCU. I normally drive in S+ auto all the time. But your are right: C can pick up speed just as well when pushed. I usually drive in a very spirited manner. When Im stopped at a light behind other cars that drive more sanely than me is when this issue creeps up from time to time 😂
