725 9g Gearbox

[kryk]

Hello everyone,

I am new to the forum.

I have an S350 2017 and for some time my gearbox is acting strange after it gets hot I guess.

When cold it is fine, when I start driving it but after a while and I am only guessing whem something in there gets hot it is not changing gears as normal at 1.400–1.600 or somewhere around there, it’s changing at 2.000 and it feels strange, like it is in Sport but nit really sporty ether.

Anyway, definitely something is wrong after driving a few hours in London’s traffic. I am a chauffeur and I use the car for chauffeuring and it takes a few hours to get to this point but most definitely something is happening when the gearbox or something in there gets to a certain temperature.

Next day when cold evening comes back to normal until it is driven again for a while and as I said from what I am guessing when gets to a certain temperature.

The car has now 70.000 miles and I was thinking maybe the gearbox service will help as maybe the oil is dirty and not that effective anymore but it does the same thing even after the service has been done.

If anyone has any idea or maybe had experienced same problems please share your thoughts.

Thanks guys !

Drive safe !

 

[Petrol Pete]

Hello and welcome . If the car has 70K on it and no history of gearbox service it is time to book it in for the service even if the transmission is not at fault.

It is showing signs of going into limp mode which is not good if you are using it to earn a living. You could get the fluid level checked and codes read but that would take almost as long and cost almost as much as getting the transmission serviced.

Let us know whereabouts you are in London and someone on here will recommend a decent independent MB specialist to you.

 

[kryk]

Sorry, maybe I haven’t made myself clear an this part.

So I thought the service will help and I have done the service on the gearbox as well as service B which was due.

The gearbox is doing the same thing after the service was done on it.

Also, a few months ago I think the gearbox has gone in limp mode or something as it was refusing to change gears until the revs were at about 3.000 with not much power and I think the engine light was on as well.

That was only one time and was sorted by stopping the car and turned off for a few minutes. After that evening was ok.

 

[Petrol Pete]

OK , understood , fully serviced and still 'acting up a bit' . Probably time to get the codes read by STAR.

 

[kryk]

Thanks Pete, yes still acting strange even after being fully served.

The dealership who carried the service should of checked it for errors I think but anyway I am just thinking to call them up and put all this on the “after being serviced” so they can carry some proper checks on it, I guess this is the best option.

 

[zipdip]

Well the stopping the car and then restarting it and the problem goes for a time is a symptom of the elctroplate in the box needing to be repaired,but get a star on it and hope it finds some codes,sometimes there are none when the plate starts acting up,you are using a MB indy or main dealer are you.

 

[kryk]

Hey zipdip, thanks for your reply, I am using a main dealer but sometimes they are worse then normal garages.

I will try to find a star to put on it maybe I will find something as I haven’t done it so far.

 

[kryk]

Hello and welcome . If the car has 70K on it and no history of gearbox service it is time to book it in for the service even if the transmission is not at fault.

It is showing signs of going into limp mode which is not good if you are using it to earn a living. You could get the fluid level checked and codes read but that would take almost as long and cost almost as much as getting the transmission serviced.

Let us know whereabouts you are in London and someone on here will recommend a decent independent MB specialist to you.

I leave in Mill Hill, NW7

 

[Petrol Pete]

Personally I wouldn't go anywhere near a main dealer for basic transmission service and repairs , they will probably try to sell you a whole new transmission ! .

If it needs a new conductor plate and a TCU plug and decent Indy will sort it.

 

[kryk]

Personally I wouldn't go anywhere near a main dealer for basic transmission service and repairs , they will probably try to sell you a whole new transmission ! .

If it needs a new conductor plate and a TCU plug and decent Indy will sort it.

You are perfectly right, I have used the Main Dealers only to service the car. I have being lucky enough not to need extra work on the cars apart from interval service and brakes which I have done myself.

Now unfortunately I may need some extra work on the car and I do not know exactly what it is.

As I said I will try to put this on the “gearbox service” maybe I will get lucky I it will be sorted easy.

 

[kryk]

So from what you guys are saying it must be the TCU and this conductor plug ?

 

[zipdip]

A decent indy will have a Star,if it is the electro plate then they can be repaired,a repaired one will go straight back into the car and work if a new one is bought it has to be coded to the car,the repair will be done by a specialist there are a few around,if a repair is needed,the problem is that you will be without the car for at least a week maybe longer,but the cost by MB standards is not huge.

 

[DSM10000]

Whilst it might be a gearbox issue there are a number of other possible causes that could explain the problem.

Various engine sensors such as the MAF etc could be faulty. The gearbox may well become less responsive if the ECU detects a problem and goes into a reduced power mode.

As said, find a good Independent who has Star and can properly diagnose the issue.

This company are close to you and are highly recommended :

Wayne Gates Specializing in Mercedes-Benz Servicing & Repairs

The Independent Merc Specialist you can trust. Based in Harrow, Middlesex servicing the surrounding areas and Hertfordshire. Call now to book

www.mercservicing.co.uk

 

[kryk]

Whilst it might be a gearbox issue there are a number of other possible causes that could explain the problem.

Various engine sensors such as the MAF etc could be faulty. The gearbox may well become less responsive if the ECU detects a problem and goes into a reduced power mode.

As said, find a good Independent who has Star and can properly diagnose the issue.

This company are close to you and are highly recommended :

Wayne Gates Specializing in Mercedes-Benz Servicing & Repairs

The Independent Merc Specialist you can trust. Based in Harrow, Middlesex servicing the surrounding areas and Hertfordshire. Call now to book

www.mercservicing.co.uk

Thank you.

 

[kryk]

Hello guys.

Nothing on the star, the garage didn’t found anything.

I was thinking that on the diagnosis it may not show up if the car is cold and the gearbox is working normal and there is a possibility that any errors to come up only when is hot and the gearbox starts acting up ?

What do you think, is that possible right ?