Slipping trans 3rd to 4th gear
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Junior Member
Joined: Nov 2025
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C43 2020
Slipping trans 3rd to 4th gear
Slipping from 3rd to 4th gear
It occasionally slip when the car shifts from 3rd to 4th gear. It increases the rpm by itself, then shifts to 4th gear. It only happens with lighter throttle.
It was already doing this before the oil change.
The oil is original Mercedes, the oil pan is aftermarket, the oil level is correct - done with xentry
After 1,500 miles, an adaptation was done, the adaptation values were fine, but it still does it now.
Will it be mechatronics bad? Xentry diagnostics is clean, no codes
It occasionally slip when the car shifts from 3rd to 4th gear. It increases the rpm by itself, then shifts to 4th gear. It only happens with lighter throttle.
It was already doing this before the oil change.
The oil is original Mercedes, the oil pan is aftermarket, the oil level is correct - done with xentry
After 1,500 miles, an adaptation was done, the adaptation values were fine, but it still does it now.
Will it be mechatronics bad? Xentry diagnostics is clean, no codes
Out Of Control!!
Joined: Apr 2019
Posts: 11,951
Likes: 6,796
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
that is UNUSUAL
Slipping from 3rd to 4th gear
It occasionally slip when the car shifts from 3rd to 4th gear. It increases the rpm by itself, then shifts to 4th gear. It only happens with lighter throttle.
It was already doing this before the oil change.
The oil is original Mercedes, the oil pan is aftermarket, the oil level is correct - done with xentry
After 1,500 miles, an adaptation was done, the adaptation values were fine, but it still does it now.
Will it be mechatronics bad? Xentry diagnostics is clean, no codes
https://youtube.com/shorts/WCFfpzdEHXc
It occasionally slip when the car shifts from 3rd to 4th gear. It increases the rpm by itself, then shifts to 4th gear. It only happens with lighter throttle.
It was already doing this before the oil change.
The oil is original Mercedes, the oil pan is aftermarket, the oil level is correct - done with xentry
After 1,500 miles, an adaptation was done, the adaptation values were fine, but it still does it now.
Will it be mechatronics bad? Xentry diagnostics is clean, no codes
https://youtube.com/shorts/WCFfpzdEHXc
You've got to troubleshoot this without open box out of car:
Read live pressure data from TCU.
Don't expect Xentry to print out fault codes.
Any shop is going to get your wallet wide open with this... any warranty of results??
> No mystery...
The current condition is based on how car was used for how long.
Lighter throttle means less pressure.
Hot frictions damage seals that drop clutch pressure that keep clutch packs loose.
Are 3-4 adaptations failing ?
What's the current blue-book value??
Last edited by CaliBenzDriver; May 15, 2026 at 03:51 PM.
Out Of Control!!
Joined: Nov 2018
Posts: 11,427
Likes: 5,336
From: San Francisco Bay Area
2019 C63CS
How many miles? On a 2020, I wouldn't expect there too be excessive clutch wear at this point. Why is your oil pan aftermarket? My guess is the pressure to one of the clutches is dropping intermittently. Don't know from the top of my head which clutches/brakes get engaged during the 3/4 shift. There are a number of possibilities besides low or degraded fluid and worn clutch packs. Possible other causes are a bad solenoid or valve body. The solenoid could stick intermittently or a valve could be bad. Other possibilities are a faulty sensor or corrupted adaptive parameters. W/o an actual diagnosis, though, it's just guessing.
Last edited by superswiss; May 15, 2026 at 05:33 PM.
