Hi everyone,

I have a 2012 Mercedes-Benz C300 with the 7G-Tronic (722.9) transmission and about 225,000 km.

When the car is cold (first start in the morning), I notice a slight jerk when shifting from 1st to 2nd gear. After the car warms up, the shifting becomes completely smooth.

The transmission fluid and filter were changed 30,000 km ago.

Is this considered normal for this mileage, or could it be an early sign of valve body or conductor plate wear?

Thanks in advance!

 

With those miles, I wouldn’t be surprised if the flex disks are past their expiry date. I’d go this route if you don’t have a transmission codes.

 

Hello @cvx5832. Thanks for your reply. I don’t actually have any transmission codes showing on the screen right now.

 

Are you really in 1st gear shifting into 2nd when it happens?

From my understanding in Sport mode the car starts in 1st. In Comfort mode it starts in 2nd. Economy mode may be the same though I dont have it so not sure what it does.

Have you switched to manual shifting to see if it happens? Start off in 1st slowly accelerating while watching the RPM's, shift into 2nd and see how it feels, keeping an eye on the RPM's.

Diagnosing transmission issues can be tricky without xentry. Heres an example below.

 

225,000 km is only “middle aged” for a well maintained 722.9 gear box.
There is a lot of excellent information and an important question in @TimC300 ’s reply.
The 1-2 upshift releases B3 and sets B1 simultaneously, making only internal brake and no clutch changes.
The 2-3 upshift sets clutch K1 while all brakes remain in their previous position.
This is why the answer to that question is important.
If the jerk is actually occurring on the 1-2 upshift, it could be a solenoid fill issue with B1 similar to that which happens with K1, but there is no service bulletin associated specifically with solenoid B1.
If it only happens when the engine is cold, and it is not offensive, then I would treat it as normal for a car of that age and not an indicator of an impending failure.
If it cannot be ignored, or if it gets worse, the problem is likely due to micro debris on the solenoid screen. This can often be remedied by removing the conductor plate at a transmission service interval and cleaning all the solenoid screens or simply replacing the solenoids (there are 5 brake and 3 clutch solenoids).
All variants of the 722.9 gear box are very durable and most problems can be solved without major overhaul or replacement.

 

I have the same symptom and was advised to replace the solinids in the transmission pan.
I have parts but won't have time to install fire a few weeks so I dunno if it'll fix it

A fluid change never hurts either.

 

I also experience this in my 2014. Never looked into it since it only happens when cold. I’ve also only ever noticed it the first time I shift from 1st to 2nd. Once it does it, it doesn’t do it again until the next time it’s cold. Following thread as I’m interested in the solenoids mentioned above.

 

That’s why I think it may be a solenoid fill time issue pure that only happens once during a drive cycle. Since it only happens once, the transmission doesn’t adapt to it. (The transmission doesn’t actually learn how you drive).