Seanhfx

Hi all,

I have a weird whining noise (mid-to high tone) coming from the rear that only happens when I'm at speed (above 80km/h+) and when the throttle is not pressed , only happens while coasting. Only seems to happen just below 90km/h to about 78km/h in all driving modes (S+,S,C and E) while coating. Say I'm coasting @ 86km/h and every so lightly tap the throttle, the noise stops, I can make the whining go away/start again just be every so lightly tapping the throttle.

I don't drive the car much in the winter and haven't noticed the noise before this winter...the whining noise can only be heard when radio is off and panorama roof is closed. I change the run flats for Michelins AS/3+ in summer 2017. Car is 2 years old in March with 13,000 kms and will be taking it in for B1 service in March. Just looking if anyone has any thoughts on what it might be?


PROBLEM RESOLVED July 25, 2019
Replaced differential under warranty.


Tks, Sean

GWSHARK

stockbmw

My 2018 C43 have been to the dealer for past month for this problem. Some people said it's the sound generator from performance exhaust package. But the foreman said it's not and changed the rear differential. The car made whinny noise at 80kmh from driver side speaker like feedback from bad grounding but now makes tad less. Foreman thinks it the propeller in the drive shaft that's also defective but the part is coming from Germany so I need to wait another month.

Seanhfx

Well I'm not sure I feel good about this or not. Let's keep this thread updated. My appt isn't until 2nd week of March but will provide any update as I get them. Oh and I do have the AMG PE if that is common among us with this noise.

MarcusDubya77

Definitely paying attention to this thread. Is this just a sedan thing or are folks with coupes getting a similar noise? Are the ones with this issue from the same factory?

user33

I had a similar issue with my 2017 C43 sedan ... whine, seemingly coming from the rear end, only at certain speeds and under certain torque (in mine, it was at about 50 ft. lb., using the engine data display). It was only related to certain speeds at the 1 torque, not to which gear the car was in. In my case, it was most easy to replicate on a flat road with the cruise control set to "one of those speeds."

The noise was present from first drive and I reported it to my dealer but suggested we wait untill the car was broken in, just in case it was a wear-in noise. It actually got slightly worse. The dealer readily acknowleged the issue after a test drive then put the car in dyno mode and, on the hoist, tracked the noise to the rear end. They talked to MBZ and it was suggested that they first try changing the lubricant in the differential (though no one really expected that to work). The new lubricant didn't change things so, after a short wait for parts, the diff gears were replaced (apparently MBZ wanted the bad one's back to study the issue).

There has been no further issue, the only real inconvenience being that my car was in the shop for 1 day each for each of the jobs -- and that I did take care to run in the new diff gears for about 1K km. My C43 now has about 22K km. and all has been well (wonderful, actually!). In my case, this was the only significant defect of the 2 my C43 had, the other defect being a control-module failure that prevented the rear passenger-side door from being opened from the inside (which fooled us for a while as we thought it was just the child lock was activated). If you're wondering, yes I do feel fortunate to have a dealer that really seems to know what they're doing and treats its customers very well. Too bad all dealers aren't of this calibre.

GWSHARK

Seanhfx

Good to hear it. Unfortunately my dealer is not as competent, SA said tech only heard it once and is related to AMG PE and turbo in the cold. The noise can be heard every time coasting between <90 to 78km/hr. I will play their game and test their theory once the temps get upto 8+ degrees.

Car is leased so I really don't care, but it will be on the service record for the new owner to determine if cold is the reason if it happens all year round.

I'll update thread if anything changes.

GWSHARK

Hi All, I meant to update this thread, last week . As stated my differential was replaced, and with the snow and March break I had not driven the car much since I got it back. Now with the break in the weather, I have been out more and the whining noise is still present at same speed, and same noise level as before. The head tech at my dealership drove it again today, and he quite honestly said he doesn’t know what it is. Long story short the car was booked back in to go over it again. Anyone else have an update or find a resolution?

Seanhfx

Well that's not great news, I was hoping you would come back with an update that it resolved it. We haven't had any warmer weather so not able to test my dealer's theory, but if it was the case about the turbo/amg PE being the cause, you'd think we'd have more people here with the problem. I'll update if it continues to happen in warmer weather.

Seanhfx

With the warmer weather, I really haven't seen that much a difference. Sound doesn't seem to last as long, now seems like 88 km/h to just above 80 km/h.

zibby43

I just saw this thread, thanks to someone directing me to it.

I just noticed the noise as well.

For those of you mentioning the Performance Exhaust as the culprit, is the noise still present with the PE in the OFF position?

My thread: https://mbworld.org/forums/c450-c43-...st-18-c43.html

Seanhfx

Yes, happens in all driving modes with PE on and off. With the warmer weather, the noise is not as pronounced or as long than it was in the cold.

zibby43

Thank you. So, is there any consensus on whether it is indeed the interaction between the PE and turbo, or is it the differential? Don't know if there have been any new discoveries on your end since April.

Also, did you get a chance to see the video I posted?

It seems strange that GWSHARK noticed no improvement until a *third* differential was installed.

stockbmw

I called to inquire about the propeller and they are still backordered. Will report back in June. Car is 6500kms and makes whinny noise but not as much. One guy had their differential replaced twice. Maybe i will suggest that too.

coladin

Could it be your tires?

zibby43

I’ve had floor mat hardware on order for months. Seems like Germany is hard up for parts right now.

That was my SA’s first guess. The frequency is similar to when I had cupping on my tires once with my C63.

But it seems strange the noise would only manifest itself under certain conditions if the tires were indeed the culprit.

zibby43

Here you can really hear it. Sound is coming from engine bay during this gradual 3rd gear pull.

Normal, or some kind of belt issue . . . or problem with charging system?

zibby43

Update: Likely some kind of belt or bearing issue.

Taking it in Monday.

user33

Turn on your engine-data display (vehicle dynamics) and see whether the whining noise occurs at a certain torque level (mine was around 50 ft lb) at certain speeds (one of mine was 80 kph) regardless of transmission gear ... if that's true, you'll likely need to have the gears replaced in your differential. Seems like there's been a number of these with C43s, mine included. Good news is that mine's been OK in the 10K km since.

zibby43

I'll give that a try. Thank you.

zibby43

Yeah, it’s present when using about 50 lb-ft.

Turns out I have 2 noises: dentist’s drill from engine bay during slow 3rd gear pulls AND whiny resonant noise when cruising at 50 mph. Resonant whiny noise goes away below 50.

The noise I get while cruising at around 50 sounds like it is coming from behind me.

user33

Sounds like you'll be in for a new set of differential gears. Depending upon how good your dealer's service people are, you might want to figure out one or more speeds/torque(s) where the whine occurs then write down a step-by-step procedure for replicating the whine and give this to them. That'll decrease the likelihood of a "we don't find any problem" response. In my case, the shop foreman asked me to come along on the "let's hear this" ride and he acknowledged it right away. They put the car into dyno mode on a hoist to verify that the noise was actually coming from the differential.

When they called MBZ, they first wanted the fluid changed in the differential, just to see whether that made a difference. It didn't, as suspected, but still worth a try (we had about a week's wait for the gears to be shipped, anyway). It's likely that mine was one of the initial cases of this as, apparently, they were going to send the gears back to Germany for examination. I'm guessing that this differential has some new aspects to it as there seem to have been a few of these issues (or maybe there was just a bad run of gears). At any rate, as previously indicated, things have been fine for the 20K km (about 12.5K mi) since the repair so kudos to MBZ and my dealer for that.

zibby43

Many, many thanks for sharing that information. All extremely helpful info. for when I take the car in tomorrow.

50 mph in 7-9th gear seems to be the sweet spot. They've already had to replace quite a few faulty components on my car, so this is just getting to be routine at this point (unfortunately).

I'm sorry you had to deal with this crap, too. Did you ever take any footage of the noise?

zibby43

Update: Had the car in today.

1) Technician drove my car and could hear the "dentist's drill winding up" noise during gradual 3rd gear pulls. I also heard the noise slightly while test driving a 2019 C43 sedan with PE back-to-back with my car.

Conclusion: Perhaps the noise was there before and the other noise from the diff had me a bit more sensitive to noise issues. Probably a non-issue.

2) Technician could not hear the faint whirring/whining noise while cruising at 50 mph (the noise likely related to the differential). Technician had me take him for a ride so he could listen as a passenger.

He could not hear the noise initially, but once we turned back toward the dealership, we weren't getting the same intense headwind we were getting in the other direction and he could hear the noise. It is fairly faint at this stage, and he credited me with having very perceptive hearing.

Conclusion: They could go ahead with trying to replace the necessary differential parts, but there is no guarantee that the noise would be better. As a matter of fact, with such a substantial surgery, there is a chance that the noise could potentially end up being worse.

At this point, so long as the noise doesn't get worse (have to have the radio off to hear it currently, and even then, you have to listen for it), I think I should probably leave it alone.

The technician was a very professional and knowledgeable dude. Definitely a car enthusiast. He was open to going with whatever course of action I wanted to pursue, and I was very impressed with how seriously he took the situation, despite the fact that the noise is, in the grand scheme of things, pretty darn faint.