LTK

I have experienced a hard to describe vibration from the rear working the tires hard upon acceleration from a stop or especially when taking a corner from a stop or traffic light. More pronounced from a stop taking a right hand turn. Almost like the rear tires dig deep, grinding into the pavement to push the car forward. Has anyone experienced similar? I'm just assuming it is the AWD. Just seems excessive when pavement is level and dry. I did experience once on my second set of tires, but I inflated higher PSI and that seemed to work. Now it was happening again, and tires were due to be changed, so I got all 4 new tires again (60K on car). It was doing it again, so I increased the PSI to 44 as recommended on the door panel from the 33 PSI inflated at the dealer, but this time it did not seem to stop this excessive use of tire grip. Any suggestions?

190Efan

Your car is still likely under warranty if you're the original owner so I would suggest you take it back to the dealer for further diagnosis that your warranty should cover. BTW, where in the rear are you feeling the vibration? Is it the entire rear or just one side? Generally such a grinding noise can be wheel bearings. Any further description you can provide will be helpful/

LTK

Thank you for your reply! So, finally have an appointment today. It could be wheel bearing, but I do not think so, I have been researching, and might be a transfer case problem, gears slipping a bit. I have found that a lot of the MBs have separate transfer cases, but not sure about the GLA250. I am going to post that question now! I certainly hope some fluid will help and not to much damage has been done. You wanted to know if my car was still under warranty, unfortunately NO!!! ARGH!! I bought new 2018, but now have 60K miles. We will see.

papaya2

Did you get an answer or resolution about this? I am experiencing the exact same thing with my 2018 GLA.

LTK

Hello, yes, the problem was fixed, but it was not cheap. It was the Rear Differential that needed to be replaced. Total estimated cost was $5640.57. One of the mechanics at the dealer mentioned that it had been a known problem on the Mercedes, and approximately a year prior there were bulletins reporting the problem, but that Mercedes stopped fixing the problem. As a result I did call MB customer care. They replied within 2 days and offered me $2000.00 towards the repair. I accepted and went forward with the repair. I was just outside the 50K mileage mark when the problem started, and always a good customer who never went to another dealer for service. If I would have brought the car in before the 50K it would have been covered fully under warranty. If you are outside warranty, you might be looking at an expensive repair. Even at an outside repair shop, it is $4,000. Good luck. I am now at 86K mileage and have no problems.


Estimate

Final Invoice of service preformed

papaya2

Thanks so much for the response. My worst fear was that the rear differential was the issue. In your photo it says the car 'hops' when turning, I wouldn't say mine is that bad, yet, more like a rumble and what sounds like tire skipping. I guess I will have to schedule a service. Maybe this is early enough that there is a cheaper solution. I will keep you updated.

LTK

Good luck, I hope to hear good news! I think the word hop and skipping are inter-changable, I could also say skip for the same thing the rear was doing. It did get worse as time went on. There was an easy test that the mechanic did to make sure it was the differential. He just disconnecedt the 4matic. It completely stopped the vibration, so he knew it was the gear box. When the 4matic was disconnected and I took the car for a test drive, it ran smooth like new, of course, without all wheel drive. I drove it like that for a week until all the parts to repair arrived at the dealer. So at the very least you should have your mechanic disconnect, and then test drive it. I was thankful my mechanic did this. Very easy to do. It was suggested on-line to flush the transmission and crank case out, but it is all connected, not separate, and the mechanic explained that it would push any broken pieces through, and that is not a good thing.

squadri1126

Glad I could find something similar to my issue, I have made an appointment with the dealer on this coming Monday. I have 43k on the vehicle but the warranty says 4 years or 50k. I hope the fix it under warranty. I am also taking to the same dealer where I bought it new. Any thoughts on the warranty if they will accept it. All my services were done at the same location. The symptoms are exactly the same like what you guys have described. Not sure if they ever changed the differential oil. Services were prepaid. Any feedback would be appreciated. I have 3 days to mentally prepare. Thanks.

LTK

If it is the differential, just have the mechanic disconnect the 4matic, the grinding will stop after a quick test drive. Then you will know the differently needs to be replaced. Honestly, shouldn't we all be reaching out to MercBenz about this known problem. Seems they dropped the ball and let us pay! For sure there are more customers out there. Let me know how you make out, I'm certainly curious if this happened to your car too. Now I have another problem. My car is at the dealer now. I brought it there for it's B service. Upon inspection they found 2 small cracks in the rear flex cap. It is going to be an expensive repair I assume. I am still waiting to hear the price. My complaint is that after the differential was replaced I kept hearing a ping back where the flex cap is. I reported it twice but told it was nothing. One customer service rep actually told me it was the fluid not reaching all the way up to the gears! Whaaat!!! Well, I let it go, they have no record of me reporting the ping, but now I certainly believe that when the differential was replaced, the flex cap was probably not reinstalled correctly, and the torque was actually the ping i heard that caused premature stress cracks. Hopefully today I will get an answer.

squadri1126

Thank you so much for your reply, I will ask the mechanic to disconnect differential, I am sure it is the same issue as I feel gears slipping on the rear. Not happy to hear your car is with the dealer again for possible ping noise which could be very well oil not pushing everywhere. Please do let us know how goes it. I will update the forum once I see the resolution and the cost associated with it. I saw one video on the tube fixed it by just changing the differential oil and resetting the learning behavior. I believe it was also a 250. I hope mercedes take care of this issue especially when it is consistent with this model. Thanks again for your time and response. Thanks.

papaya2

An update on the situation with my car. I brought it into the dealership and described the issue. They did some troubleshooting, which frankly seemed a lot like he found this exact forum post, and they flushed the differential / transmission fluid. This has pretty much eliminated the sound / rumbling entirely. This is however not really a fix, so much as a bandaid, and the grinding will likely come back over time, so we will eventually need to replace the differential.

My guess as to what is happening, is that some part of the differential is breaking down, resulting in debris interfering with the gears, causing the rumbling. Flushing the fluid has removed the debris, and probably slowed the rate of break-down.

As a side note, does using eco-mode disable the AWD? If so, that would stop the issue.

LTK

Hi, let me know how long the fluid change actually helps before the grinding starts again. Even though I have a new differential now, a Mercedes repair garage near me has suggested I replace the fluid every 30k miles. So I am going to do that, since this is a known problem, and I still want to keep the car. How much was the fluid change for your car, and did you have it done at a dealer?

Also, the AWD does not turn off in the dynamic select drive control of ECO mode. To my knowledge, only the mechanic can disable the AWD, which as I mentioned stopped the grinding, but then I had no AWD. Living in the Northeast, I really want the AWD. If I lived in the South with no snow, and the differential broke again, I would consider just disconnecting, and keeping the car without. The fix is to expensive again, so the fluid change now is the only cost effective thing to do.

papaya2

So I just started to hear the noise again. Not even 6 months later. The thing is, I noticed it immediately driving home after getting the summer wheels put on. And when they replaced the fluid, they also changed the wheels over. My winter tires are on 18in rims, my summers are on 19in. Is this a coincidence, or could the rim size play some role in this?

LTK

Oh my!. Maybe it possibly could be the bigger 19" rim size. However, have the mechanic disconnect the AWD. This is the first thing to diagnose the differential problem that my mechanic used.
Once the AWD is disconnected, no noise or grinding. It only takes 10 minutes for them to do this, so I hope the dealer will help you out and not charge you. Please let me know, as it will help all of us with this very costly, known MB defect. Easy test to do before a costly repair! Thanks!