DCTs are performance gear boxes. A lot of software has been developed to make them drive gently, mimicking a torque convertor automatic. But at the end of the day you have a computer attempting to feather a clutch pedal.

These transmissions perform best when they are driven aggressively. Otherwise they will buck and stutter a bit from time to time. It's just their nature, especially when downshifting a you coast to a stop. Brake / stop more aggressively and the problem diminishes and generally completely goes away.

 

DCTs are performance gear boxes. A lot of software has been developed to make them drive gently, mimicking a torque convertor automatic. But at the end of the day you have a computer attempting to feather a clutch pedal.

These transmissions perform best when they are driven aggressively. Otherwise they will buck and stutter a bit from time to time. It's just their nature, especially when downshifting a you coast to a stop. Brake / stop more aggressively and the problem diminishes and generally completely goes away.

You absolutely correct and bang on the nail I’ve noticed that too unfortunately when people don’t know what they’re are buying and they notice the characteristics of the car they Automatically think that there is something wrong with the car which is natural for someone to think that But then start panicking in the car sorts of garages spending lots of money for them not to be able to find anything wrong with it That’s why if someone is going to purchase one while it’s stationary and running put it into reverse and drive and if there is a clunk noise then I wouldn’t be purchasing that one because it could be a gearbox problem i’m no expert but I just did a bit of research after I bought mine when I thought I had a problem with it but I’ve spoken to other people with GLA 45 or Mercedes 4Matic and these do the same thing so it all put my mind at rest 👍👍

 

The dual-clutch prepares the next for the next gear based on how you are driving. If speeding up, it prepares the next upshift gear to be ready to engage, or if slowing down, it will prepare the next downshift to engage. If you are slowing down and the clutch is getting ready for the downshift and you change and hit the pedal to speed up, you can get a rough shift, and what goes with an unplanned change shift of gears.

 

Start by changing the diff oil. IMHO this needs to be done every 10K miles. Others on this Forum have found an oil change cured their problem. No guarantees, but an easy place to start.

 

Thank you for your quick response. I have scheduled an appt with the service center. I will look for a latest thread but I couldn’t find any other 2024 GLA thread so will start a new post for 2024 GLA for general observations and hopefully new members will chime in too

 

I have noticed a similar clunk when coming to a stop in D on my GLA and also in N, but the latter is much louder and can be physically felt, which I have noticed on our non-DCT GLE too.
I did the pedal reset yesterday and it has reduced/nearly eliminated any clunking in D, most unwanted transmission behaviours, and maybe 10% of the DCT's indecisiveness when picking which gear to be in.

 

So do you think that outside temperature would affect it then? Is this a problem that should only happen in the winter or the summer?

 

i'd say the clunk would happen more often and for longer duration in winter because it would take longer for the fluids to get up to temperature.

i'm keen to see what other owners experience and if the majority of you don't have this issue, then it blows the theory i believe out the window and i should take mine back to the dealer for a check up...

 

That's what i've noticed too and usually it takes 10-15 minutes of the engine running and another 10 of driving for everything to feel 'worked-in' with most of my vehicles in winter.

 

You might look into the dual clutch . I had to have mine replaced

 

For sure. The trans shines, or at least doesn't disappoint, when driven hard. Not a good fit for the 250, marginally.more acceptable in the 45. The great 8 speed ZF makes all the sense in the world for both cars honestly. They make a transverse one don't they?

 

Moving forward ... motor oil changes at 5K miles with diff oil at 10K miles (every other oil change). These are both easy DIYs that will save you more than enough money on the first time to pay for the tools and more.

Then we get into what kind of motor oil and Ceratec or MoS2 or not. This can get emotional!!!!!

The diff gets the MB oil regardless of the high price.

 

I have a CLA45 2017 with the similiar clunking noise that people were describing here. When coming to a stop (rolling), the clunk can be heard downshifting mostly from 2nd to 1st. Had diff oil changed, had adaptation done, changed the transmission oil. Finally, went to authorized MB service to check if something is wrong with the software and asked to update it. I was informed that the transmission software was the newest, but it wasn't compatible with the main computer software. It was fixed and I was assured that the issue should be solved. They also did diagnostics 2x times (when buying the car and after the recent visit) and from their point of view the transmission works ideally. Result: thumping/clunking noise can still be felt going to a full stop. Maybe not so noticeably, but it's still there. Otherwise, the gearbox works fluently (upshifting, downshifting in an aggressive manner). While reading previous stories I really started to think that maybe it's the way it should be, due to the nature of the transmission. However, it still seems weird. Maybe someone else still has tips and what to try next?

 

Dual clutch transmissions are meant to be driven in a sporty manner in order for the computers to rev match and fluidly operate the clutches. If you slow down gradually often times the downshift to first can be harsh. It's a bit in the nature of the beast.

That being said, you can adapt your driving style to minimize this. Have you tried slowing down later and decelerating harder when coming to a full stop?

As with anything mechanical, some of these transmissions are smoother than others. Add in the computers attempting to mimic human inputs on the clutch pedal and a lot can happen.

But on line communication can leave a lot out. Sorry if the above is off mark.

 

What is that pedal reset you ar mentioning?

 

Reset Transmission Adaptive Learning Pedal Travel

 

Ive got the same problem with my 2015 Mercedes gla220d 4matic, although the noise is becoming more consistent even once I've been driving for 1hr+. Should I be concerned that the rear diff is going or has already gone?

 

Start by changing the diff oil. That has fixed the clunk for many on this Forum.

 

Did this twice, back to back. Did nothing.

I decided to sell it. It was getting on my nerves. Great car otherwise. I'll miss it. Now I have a 2023 X3M, soon to have a JB4 so that it can have 600 at the flywheel (according to BurgerTuning )

 

There seem to be a number of different problems people are having causing the 'clunking noise.
My understanding is it only occurs when there is a shift from power to drag felt from the rear. It seems as it the tolerances from the complex gearing combine when to power shifts from the engine driving to when the engine is braking. There is s knock type of sound, but only at very low speeds. Above was mentioned as a slack in the PTO gearing to the rear prop shaft. In the mix would be any slight out of phase dual clutch application. I can't remember when, but I have felt the same when using a farm tractor when there was a shift between the engine powering to the ending braking especially at low speed. I have a 2016 45 26K Kms.

 

There seem to be a number of different problems people are having causing the 'clunking noise.
My understanding is it only occurs when there is a shift from power to drag felt from the rear. It seems as it the tolerances from the complex gearing combine when to power shifts from the engine driving to when the engine is braking. There is s knock type of sound, but only at very low speeds. Above was mentioned as a slack in the PTO gearing to the rear prop shaft. In the mix would be any slight out of phase dual clutch application. I can't remember when, but I have felt the same when using a farm tractor when there was a shift between the engine powering to the ending braking especially at low speed. I have a 2016 45 26K Kms.

Yes, quite similar to a farm tractor shuttle shift.

 

I just had my diff (and trans) replaced. The diff clunk is still there...unreal.

 

Have you taken it to the dealership for a check up yet? Odd that it goes away after a while.

 

I have the same issue. I thought it might be an exhaust burp initially, but it is definitely a clunk in the first few minutes of driving. I have less than 3500 mi so far. Have not yet had it in for service.

 

the dealer told me it was the nature of the car. the glb250 has a manual transmission controlled by automatic shifting computer software. they don't sync up. They are waiting for a software update to try to eliminate the problem.... you are NOT alone!

 

i've got the same issue and it goes away too after driving for a bit.

i dont know how true, but the research that i've read up on says it's the cold fluids and the rear diff disengaging (iirc) that causes the clunk. once the fluids are up to temperature and at the right viscosity, the issue goes away.

 

I've only had mine since June, so it's only been summer months so far.

 

Would this cause damage over time?

 

Does it go away once the Eco start/stop kicks in? Just guessing here that it might be related as the Eco doesn't go into effect until the engine is warmed up.

 

Just wanted to provide everyone with a quick update. I scheduled a service appointment to have the clunk looked at. While I was explaining the issue over the phone, service asked me if I had any issues with hard downshifts as well. After reading up all about this, I assumed it was just the way the car ran because I have certainly noticed it, but it's been identified as "normal" operating conditions especially in sport mode and with the DCT.

Anyways, I dropped the car off this morning and got a call later in the afternoon saying there was a service bulletin to update some software, which they did. All of the issues have completely gone away, no more clunking when coming to a stop, and the transmission is SO much smoother when coming to stops in sport mode.

I will say that the biggest difference that I noticed immediately was the responsiveness of the throttle/pedal primarily in first gear from a stop, but also in all gears and speeds. There was so much "play" with the pedal before the car would actually go, and it took a lot of feathering on the gas and pressing down over an inch before I would accelerate. This issue has been identified several times on these boards and is common with the CLA too but I have to say that after the software update they performed, it was 100% better.

Long story short, if you are experiencing any of these issues, make an appointment!

 

I dropped the car off this morning and got a call later in the afternoon saying there was a service bulletin to update some software, which they did. QUOTE]

Do you have a record of the update on your service receipt? Is there a MB bulletin number listed?

The reason I ask is that I had my GLA in for the A service recently and asked about a transmission software update having seen that mentioned on this and other GLA boards. The service advisor told me he looked in the system but didn't find any updates available. This is confusing to me, making me wonder if my local service advisor is correct, incompetent, or lying. My GLA250 was a July 2014 build, so is unlikely to have latest software. On the other hand, have not noticed any clunking, and transmission shifts smoothly from dead stop.

 

I'm having a similar issue - audible clunk under the same circumstances. Brand-new 2016 GLA 45 AMG, 1300 miles and I broke it in very carefully. Didn't even know what 'kickdown' was until this week so pretty unlikely that I ever did it during the first 1000 mi. Guess I'll bring it in for a checkup...

 

Hi there just wondering how you got on with this issue as my car is getting checked out today?