[Artemis]

Extracted several posts from the lengthy "Updated car differentials" thread reporting about the 'soda can crunch noise' issue.

Enough similar experiences reported worth a little compilation in a separate thread.

FWIW, from the BMW rear axle differential replacement 0033990100 'Technical Action' doc (July 19, 2016) (see here):

"Auswirkungen: Die Lamellen im Hinterachsgetriebe verschleißen sehr schnell. Es kommt zu massiven Geräuschen im Hinterachsgetriebe."
"Effects: the rear differential blades wear out very fast. Massive noises from the rear differential."

Makes you kinda wonder whether this might be a sound explanation [pun intended] for the weird metallic ramble that several M2 forum fellows reported about (an occasional, peculiar grinding/screechy rambling noise coming from the rear underside). Or is it totally unrelated to the ongoing rear axle differential replacement of several ///M cars ? We don't know yet.

Personally I heard the 'soda can crunch noise' already many times on my M2 (April 2016 build - approx. 12K kms clocked). Though, to be perfectly fair with all of you, I never experienced it affecting the driving behavior of the car.

Why calling it an "issue" rather than a "gimmick" ? Well, it is definitely a nuisance, rather unsettling each time it takes you by surprise. Recurrent, but no frequency pattern + you cannot provoke it (making it hard to show it to your dealer).

So, should you ever hear this noisy gremlin in action (lasts only a brief moment; sometimes happens twice [brief sequence]), do know that you're not alone + nothing fell off your M2.

LAST UPDATE: OCT 4, 2016

Originally Posted by Artemis

I already heard many times (30 times or so in 7000 kms) some strange grinding noise coming from the back underneath.
It's a screeching metallic sound of some metal part rubbing against another metallic part for more than an instant. A kind of metallic rambling (or some rambling inside a metallic box) for a few moments (a second or so) rather than just some brief clunk. Happens at random, sometimes twice right after each other. Mostly when the car is not under load (for example cruising at slow speed or after coming out of a turn). It sounds as if some part moves in a controlled way from one side to another (opening or closing of a part) but with an awful rambling noise. Always exactly the same sound. I even got used to it ("Oh, here it goes again"). As far as I experienced, no impact on the driving itself.
Very weird. Never heard that on any ///M car I ever drove. And no, it ain't the opening/closing of the butterfly valve of the M Performance Exhaust (totally different sound) nor the notorious 'cow bell sound' phenomenon caused by pebbles that got inside the brake system. I suspect the diff performing weird stuff.
I told my dealer. He reported it to BMW. He saw in the system a notice about (normal) screechy sounds at slow speed during break-in: bedding in of the brakes during the first 500km. Definitely something else.
My car is an early April 2016 build.

Originally Posted by Nick2016M2

I heard the same thing when pulling out of my driveway once. Definitely did not sound like any sort of normal noise.
Early May build

Originally Posted by LinkF1

I have the same experience, also an early April build. I haven't been able to determine what causes it or force it to repeat so I can't really complain about a sound that almost never happens.

Originally Posted by gthal

I've heard it myself and also heard it on my M4. I am almost certain that what you are hearing are pebbles lodged in the dust cover on the brakes. They screech for a second and then fall out. I could be wrong, but it doesn't sound like a cow bell and I'm sure it's this. Also, happens sometimes driving in a straight line where the diff would not be relevant like it would in turning.

Originally Posted by gmzanatta

Actually, Artemis may have a point, here is a direct quote from my guys:
"My master technician suspects that the differentials may grow noisy with time, this is something the factory would only have noticed after some driving. Again, this is all just speculation."

Originally Posted by OrangeCrush

I have been hearing this a lot and just chauked it up to being the cowbell-rock in the dust shield. Now I'm not so sure because I have heard this 10 times more in the couple months of ownership of the M2 than the 5 years with the 1M. My car is an early HEA [dealer demo] car delivered in April. It sat at the port for a month or two before delivery. Could it go this far back?

Originally Posted by Adem1534

I've heard it about 5-10 times in 2 months. It's exactly how it's described there. Slow speeds during light breaking. Not too worried. If anything's wrong it'll be under warranty, but I don't think it's not something that would have been missed during testing.

Originally Posted by Twix

Artemis If your car was built early April like mine, I wonder if I too have this problem. One of the days on the M tour I had to pull over because of a gnarly metal on metal sound. I had the M engineer drive the car around the lot and he said it was just the brakes. Brakes shouldn't make any noise when they're not in use if they're sorted out properly.
Once I get my car next Friday, I'll take it for a decent drive up in the mountains or something to really put the differential in motion. See if I get any noise.
After reading your post, I'm surprised that the issue goes back this far. Maybe it's not just a bad batch of parts, maybe it's the design itself.

Originally Posted by Prodigy.

Hmm I have always thought it was stones caught in the brake shields but maybe not, mine is a March build.

Originally Posted by reppucci

For what is is worth....
my M2 is may 30 build, took delivery July 6. I will be getting a new diff swapped in by my dealer at some point. Confirmed by BMWNA.
I only have ~ 500 miles on my M2; travel work etc...., but I do recall on 2 occasions, before knowing of the diff "STOP delivery campaign" announced July 20, hearing a screech from the rear during a low speed turn! Very transient, fleeting, lasted less than a second! I remember members mentioning this on prior posts as "you will know when you hear it" I thought to myself yup that is probably it
If this screech is part of the basis of the diff "STOP campaign" Artemis has a point...this may go back quite a bit!

Originally Posted by OrangeCrush

I think it might. If the noise I am hearing is in fact the diff, then this goes back to the Feb/March builds. So basically...all of them!

Originally Posted by koastal

I took delivery of mine om May 6. It makes random noises metallic / clanging noises on a irregular basis.

Originally Posted by ajvdh

Just to add to the list: My car is a February build, and once in a while I hear a brief grinding noise from the rear. Kind of like "GRANK!"

Originally Posted by Prodigy.

This is exactly what I've been hearing, I've been passing it off as stones getting trapped but after hearing the videos that MTHRAR posted I've realised it sounds nothing like those.

Originally Posted by Fuman

I've had the same loud metallic thud/grank at about 600km from delivery. It happens when the engine was at autostop, I had to accelerate hard, the auto start kicked in, and the loud noise thud/grank was produced. I've since coded out the damn autostop.
[...] Overall it sounds like marbles in a tin -- not that loud but obviously noticeable in the cabin. Let's just say I wouldn't drive without music in the background. Pretty disappointing for a rather expensive German car in AU. BMW AU seems to think it's ok hence little effort in continuation. I've also run out of motivation to convince them - I do have other better things to do.
I'm just living with it. Waiting for more community feedback. Apart from this tin can transmission, I do love the M2.

Originally Posted by pim85

Did anyone find out what's causing this sound? I have a MY17 not affected by the diff recall, but I also hear this sound now and then.

Originally Posted by pim85

Mine wasn't affected by the recall apparently (built 15.07), and sent to Norway after that. However I do hear a sound from the back occasionally. Do any of you with a fixed diff. Hear this? It's apparent for a split second, and the way others have described it as driving over a cola can is spot on. Could this just be a normal sound for this car??

Originally Posted by CAVU

My rear diff was replaced prior to delivery on August 19. With only 120 miles on the odometer, I've heard this sound 4-5 times already, and always while turning a corner when you would expect the rear wheels to be turning at slightly different speeds.

Originally Posted by Prodigy.

I've also enquired again at my dealership, I informed them of the metallic noise 2 days after picking up my car but that was long before the issue was announced so emailed them again stating I think the noise could be linked to this diff recall. They replied saying they will look into it but that was a week ago.

Originally Posted by sarcastrix

Picked my new car up on Friday - had only gone a few miles before I heard the first crunch, whilst pulling away from lights in straight line.
My delivery had already been delayed a couple of weeks due to the diff issue, so maybe they didn't change it after all...

Originally Posted by sarcastrix

That's the certainly the way it looks to me. My car has a production date of early July (it's got v.5) yet wasn't delivered (to Sweden) till last week, therefore it must have sat around somewhere in those missing weeks. First 'crunch' I heard was with less than 50 miles on the clock.

Originally Posted by jlapicki

Yes, the August builds are still affected......got my first definitive crunchy screech last night with about 150 miles on the car.

Originally Posted by MrBucket

I did hear a weird metallic noise coming from the rear of my car today, but I also had my old M235i exhaust and intake in the trunk so it could have just been them moving around and making the noise. I'll have to take them out and listen for anything else.

Originally Posted by Swimfanrick

I just picked up my 2017 M2 (July build, week 30) yesterday and in the first 175 miles heard the can crunch despite being told by both the dealer and Genius that my car did not have an affected differential.

Originally Posted by MrBucket

Ok, my car is definitely affected by this differential issue, I'd heard the sound once last night, but then about 5 minutes ago it did it twice in quick succession driving about 10 miles an hour. It sounded exactly like crunching a soda can. First showed up at 663 miles and I've heard it twice in 5 miles since then.

Originally Posted by David1

August build on mine and no paperwork for the diff at about 550 miles and just had some nasty crunch noise from the back. Is this a normal noise or is the bad diff noise?

Originally Posted by MarkR262

Took delivery on my 8/29/2016 build M2 on Friday, 9/30. Got to witness the soda can crunch diff noise several times today. Started at 200 miles. Experienced it 4 more times over the next 25 miles. Sometimes sounds like something metallic dragging on the pavement for a split second. Bummer.

Originally Posted by Prodigy.

I've been able to catch the noise a number of times on my dashcam, I'll try and upload a short clip to YouTube in the next day or so.

Originally Posted by David1

It is so loud and damage sounding that you get out of the car to look for parts on the ground. I didn't believe it until I heard it in mine.

Originally Posted by CrashFL

I've experienced the "oh sh!t what part of my car is dragging on the pavement" noise once in the 1,500 miles I've driven. It was early on, and it hasn't repeated, but it was pretty unpleasant.

Originally Posted by David1

it sounds like the diff leaves parts on the ground.

Originally Posted by pim85

I have an early 17 with this noise. Dealer say this sound is normal to the M2. No recall as far as I know and I did 2000 km service.

Originally Posted by David1

It is not normal and I have worked on diffs for a loooong time. It's a different sound, but not normal. To me, it is not a ring and pinion issue but more likely the variable lock up unit in the diff that puts pressure on the spider gears.

Originally Posted by Artemis

Checked a German M2 forum and some equally report about the grinding/rambling noise, described by some as "the noise of driving over a Cola can". So here we go: the can crunch noise...

"I already had several times a rambling noise, as if I drive over a Cola can or something alike. I personally noticed it, for example when I drive at low speed with open windows through the city. Pedestrians looked back, startled, as if I had driven over something, though I hadn't. I cannot yet pinpoint this, as I don't know where it comes from. I cannot provoke this noise. Happens with cold and warm [engine] circumstances. Has anyone an idea ?"
"Ich hatte schon mehrfach ein klapperndes Geräusch, als wenn ich über ne Cola-Dose oder so etwas fahre. Ich habe es selbst festgestellt, wenn ich z.B. bei langsamer Geschwindigkeit durch die Stadt mit offenem Fenster fahre. Fußgänger schauten sich schon erschrocken um, als wenn ich irgendwo drüber gefahren bin - was aber nicht geschehen ist. Kann ich leider nicht näher zuordnen, da ich nicht weiß woher das kommt. Ich kann das Geräusch auch nicht mutwillig erzeugen. Passiert in kaltem und warmen Zustand. Hat jemand ne Idee?"
source: here

"I also already experienced this one time; I immediately activated my hazards and checked under [the car], though have not seen anything; when I resumed driving I briefly heard it again and nothing ever since; really weird :/"
"Ich hatte das auch einmal, sofort Warnblinker an und runtergeschaut, es war aber nichts da, beim weiter fahren war es auch kurz wieder da und seitdem nichts mehr, echt komisch :/"
source: here

"Now that your saying this, I also remember such a slight rambling while driving, as if something was rattling. I immediately stopped, but did not find anything suspicious. I drove on and the noise was gone. Really strange."
"jetzt wo das sagst, erinnere ich mich auch an so ein leises Scheppern während der Fahrt, so als ob da irgendwo was klappert. Ich habe sofort angehalten, aber nichts Verdächtiges gefunden. Bin dann weitergefahren und das Geräusch war weg. Wirklich komisch."
source: here

"But it really sounds brutal, as if I drove behind a "Just Married" car with Cola cans. "
"Aber das hört sich echt brutal an, so als wäre ich hinter einem Hochzeitsauto der Coladosen hinten hat "
source: here

"That's exactly how it sounds !"
"genau so hört sich das an!"
source: here

ADDED

Two brief dashcam videos courtesy of forum fellow 'Prodigy' showing the 'soda can crunch noise':

00:06

00:03 and 00:10

See also this thread http://f87.bimmerpost.com/forums/sho....php?t=1350056 referring to PuMA # 61199185-05: