David Cook

I have a 2017 C200, I hope here is the right place to post as mine is an estate (W205?) If not please point me in the correct direction, I could only find 'sedan' listed.

Anyway it is fitted with the 7G Tronic automatic gearbox, and has about 26000 miles since new, and we've owned it from new.

It has only ever been serviced by the main dealer, the same dealership who sold the car. The last service was only a month ago and their only comment to mention that the tyres are 2/3 worn.

We don't do many miles, especially now as mostly we use it for longer journeys which are relatively infrequent but for some time I have been thinking the gearbox is not its usual self, that is to say usually gearchanges are interceptable unless you're really pressing on and now it's often jerky, slow to kick down for overtaking and there's a notable thud when slowing down as it changes down gears.

We just got back from a ~350 mile round trip over a long weekend and on the journey home (170 miles, no stops but bad traffic) it was really jerky, seemed slow to react when asked to overtake and notably unrefined in downshifts when slowing for junctions. It also returned 5mpg less on the way home than the way there, although my driving style whilst terrible hasn't changed.

I don't have any MB specific obd reader (is there one that doesn't cost the earth?) So I have no idea what the codes are if any - there are no warnings or indication of issues on the dash when driving.

Is there a service schedule for the 7G Tronic, oil or filter changes I should be checking that the dealer has been undertaking? If it's in need of a software update that could help I don't understand why that would cause the issue to start?

Alex AL

You don’t need an MB specific scanner, but you will need one that will read transmission codes, a decent one is about $500. I had an issue in my 2015 C300 where the transmission would jerk quite bad but it would only happen under hard acceleration, otherwise in normal driving it was perfectly fine. The dealer replaced some kind of transmission solenoid under warranty which solved the issue. Low fluid level can also cause the transmission to act up but there is no easy way to check the level in the W205.

David Cook

Thanks for replying, I think I will have to bite the bullet and at least call the dealership to find out what they did in the last service, perhaps best case scenario it had a scheduled oil change for the gearbox and they've underfilled it...?

Are there any recommended OBD readers for Mercedes? Or any particular reader makes that show gearbox codes?
Also will an OBD reader show the gearbox oil level?

Alex AL

if you are looking at a specific OBD reader there should be a list of vehicles that is supports somewhere in the description. I don’t think it will show you a specific oil level but will say something like “fluid level ok” or “fluid level low”

TwoC400s

@David Cook have you tried doing the MB transmission adaptation reset?

matt.jessop

Sounds similar to an issue I had - EGR valve, caused very similar symptoms. I bought an OBD reader from amazon for about £25 and it read the codes without a problem - I then passed them on to my MB garage.

Probably worth trying before going to Merc. This is the OBD I bought

David Cook

Should I be embarrassed to admit I don't know what that is?

David Cook

Isn't EGR a diesel related issue? Ours is a petrol, I'm not sure if they have EGRs (do they?).

I have rung the dealership now, I have an OBD reader but I have never used it on the C200 and was a little nervous of doing something that then may make the dealer have an excuse to tell me it's my fault.

On the possible plus side at it's last (5 year) Service last month the dealer did say they had serviced the gearbox, giving me an ideal opportunity to let them know it isn't working correctly and ask them to check it.

I'm hoping that they maybe underfilled it a little, and maybe it just needs a top up which they will agree is their responsibility.
On a related note would doing ~500 miles (not gently driven) cause any damage to the gearbox?

chassis

There is no “reset” possible without XENTRY. Resetting adaptations in XENTRY is risky business because of physical wear in the clutch friction surfaces and hydraulic system, the very reasons for adaptions in the first place.

The 7G is generally a below average transmission. The 9G isn’t much better. MB boxes are sub-par compared with ZF and Aisin.

Recommendation: get the fluid replaced by the dealer and live with the transmission performance.

matt.jessop

You are 100% correct, I didnt spot it wasnt a diesel - my apologies Hope you get it sorted soon

David Cook

Well I have an update!

The car was with the dealer for two days, and we are currently awaiting it's return.

They say it is fully functional again, apparently it was a software issue?

Obviously I may change my tune if it comes back and all is not well but I have to say our local dealer (Sanddown Mercedes Basingstoke, England) has been excellent. They called to give an update and ask to retain the car for a second day, and collected/dropped off to us at home.

DYC300

What is the reason to get the fluid replaced by the dealer vs an indy? Normally, it is advised to stay away from dealerships due to their high price.

I need to start looking around to get my 60k service, but may do my transmission service earlier since I'm getting jerky 2nd to 3rd gear shifts. :/

chassis

The dealer has the training, procedure documentation, tools and materials (oil, gaskets, etc.). If you trust the indy, go for it. Transmission service is tricker than an engine oil or air filter change. I am willing to pay dealer prices for transmission fluid replacement.

DYC300

That's a very fair point. I think for something you do 2x or maybe 3x the life time of your car, it is worth doing it right and paying a slight premium.

I'm glad I asked!

benzdude

I have severe rough downshifts to (5th to 4th) in the winter.It almost feels like the car is braking, it's that rough. Only happens when the engine is first started and only lasts until the engine get hot. its very annoying and the dealer is no help. (sad face)

DYC300

Do you have rough upshifts from 2-3 or 3-4?

benzdude

Upshifts are fine. Just down when engine is cold.

DYC300

To clarify, when you say "fine" are your upshifts buttery-smooth (can't notice changing gears)? Everyone's definition of fine can vary, so just wanted to see.

I swear my upshift jerks weren't there when I got the car a year ago. But I started noticing it recently. I'm taking my car into the dealer on Wednesday under CPO warranty but I am afraid they will just tell me everything is OK and charge me a diagnostic fee.

benzdude

​​​​​​Ok to be clear and precise, this is all in C mode. When i say fine, i mean not jerky, not rough, nothing to cause alarm. I am pretty sensitive to the car by now so I can tell.

In S and S+ mode the shifting up can be a bit shaky, but its sport mode.

The dealer told me there is a software update for the 2 to 3 up shift problem, you might want to ask sbout that.

​​​​​​Yeah, i asked them to check the front suspension during A service and they charged me $190 just to look. oh well.

Plus i didnt win 1.2 billion lotto yesterday (G-wagen!)

DYC300

Appreciate it Benzdude! I hope that the dealer can apply the software update to fix the upshift issue.

And yeah I didn't win either... maybe next time?