Thunk/clunk sound when decelerating/accelerating

[jnthn]

Hi there,

Recently I've been noticing that when my car decelerates or accelerates, at times I hear a thunk sound near the rear. It sounds like it is under my car and kind of sounds like metal on metal.. I was wondering if this is normal? I am wondering if it is the clutch disengaging and re-engaging? But metal on metal always is bad right? It's not a high pitch clink or screech, but thick metal clunk.. lol

I just wanted to ask if anyone has this before I take it to BMW

[Poiseuille]

Your car needs to go to the dealer for service, and fairly soon I'd say. See attached recall for example. Doesn't mean this is the specific cause of your complaint, just to point out you ought not ignore noises like that.

[tropicalypso]

Mine does it too. Only when in Efficient/Comfort settings. Its intermittent.

[RealtorReeceM3]

Originally Posted by tropicalypso

Mine does it too. Only when in Efficient/Comfort settings. Its intermittent.

My 2018 is doing this.

[CigarPundit]

I haven’t heard your car, but I wouldn’t jump to any conclusions. This car makes more NORMAL noises than any car I have ever owned. It clunks, it whines, it clicks. It makes noises when you shut it off. There is a lot of audible stuff going on in this car both during and after operation. By all means, take it to the dealer and have them take a listen, but I’m telling you that this car makes a lot of sounds that other cars don’t seem to make even when everything is perfectly normal.

[bluek]

yeah I've heard a metal/metal sound like a muffler dragging on the ground. happens every now and again maybe when accelerating but only at slow speeds. actually just took my m4 in for a different issue but mentioned this to the service rep.

[CigarPundit]

The scraping metal sound may be a rock stuck in your brake rotor shield, which is a fairly common issue. Not harmful really, just annoying. I’ve also found that the brakes squeak sometimes in reverse, but it’s nothing to worry about. The car is kind of quirky when it comes to noises, especially if you have a perceptive ear.

[CigarPundit]

Mine also made a clicking sound from the front wheels when turning. You could hear it at slow speed with the window open. Nothing to worry about, but there is a fix for it, which I recently had done at the dealer.

[mfurse]

Is it like this? This is me mildly accelerating in manual and going from 2nd -> 3rd. You can hear the noise and it's repeatable.

[jnthn]

yup it's exactly as you guys say and what the video sounds like.

I better take it to the dealer then if it's related to the loosened bolts.

thanks for all the help guys

[mfurse]

Originally Posted by jnthn

yup it's exactly as you guys say and what the video sounds like.

I better take it to the dealer then if it's related to the loosened bolts.

thanks for all the help guys

So...after that video I actually took it in to the
Dealer who was awesome, they raised a PUMA case and the noise was identified as a prematurely worn synchro on 3rd gear. BMW authorised a new transmission (they seemingly don't open these things anymore) and had it swapped over.

[jnthn]

Originally Posted by mfurse

So...after that video I actually took it in to the
Dealer who was awesome, they raised a PUMA case and the noise was identified as a prematurely worn synchro on 3rd gear. BMW authorised a new transmission (they seemingly don't open these things anymore) and had it swapped over.

damn that's awesome. I'm going to use those exact terms to leverage my own new transmission thanks for the update

[mfurse]

Originally Posted by jnthn

damn that's awesome. I'm going to use those exact terms to leverage my own new transmission thanks for the update

I would make sure it's repeatable as the technician had to drive the car with me in it and get it to make the noise. Fortunately hot or cold, it would do it every time from 2nd to 3rd and when popping it into neutral whilst going along.

YMMV with any of these noises or clunks - sometimes it's considered normal othertimes it's a replacement. Warranty is a must on these higher performance cars!

The transmissions are pretty robust though - they're used on the F10 M5 with more tq and hp and there are M3s with 100K+ miles on them which are shifting perfectly still. I can only imagine that a limited few trannies would have had faults like mine, fortunately the noise showed up quickly as I had only done 16,000 KMs.

[FlyinRhy]

Originally Posted by mfurse

I would make sure it's repeatable as the technician had to drive the car with me in it and get it to make the noise. Fortunately hot or cold, it would do it every time from 2nd to 3rd and when popping it into neutral whilst going along.

YMMV with any of these noises or clunks - sometimes it's considered normal othertimes it's a replacement. Warranty is a must on these higher performance cars!

The transmissions are pretty robust though - they're used on the F10 M5 with more tq and hp and there are M3s with 100K+ miles on them which are shifting perfectly still. I can only imagine that a limited few trannies would have had faults like mine, fortunately the noise showed up quickly as I had only done 16,000 KMs.

Hi! Did replacing the transmission with a new one solved the problem?

[mfurse]

Originally Posted by FlyinRhy

Hi! Did replacing the transmission with a new one solved the problem?

Yes. Good as new.

[joooiiiiii]

Originally Posted by mfurse

Is it like this? This is me mildly accelerating in manual and going from 2nd -> 3rd. You can hear the noise and it's repeatable.

Wow, okay that sounds pretty bad. Mine just has a slight 'push' or 'shove' but I'll have to pay attention to my transmission today to see. Glad to hear that BMW covered it.

[JeffB-M3]

I get all sorts of noises from the clutch / transmission area. I sometimes get a clunk like in the video. I also get odd metal-on-metal rattling / grinding when at a low speed and starting to accelerate easily. Sometimes struggle to get the car in 1st gear. Some of the items feel like synchro issues and others I'm still clueless on. The car is still under warranty and have had dealer check for all of them but got the "unable to reproduce" report. I'm doing an auto-x this weekend which will be the first time really pushing the car since I got it a couple months ago. I expect the gremlins will start to surface at the auto-x event.

[mfurse]

Originally Posted by JeffB-M3

I get all sorts of noises from the clutch / transmission area. I sometimes get a clunk like in the video. I also get odd metal-on-metal rattling / grinding when at a low speed and starting to accelerate easily. Sometimes struggle to get the car in 1st gear. Some of the items feel like synchro issues and others I'm still clueless on. The car is still under warranty and have had dealer check for all of them but got the "unable to reproduce" report. I'm doing an auto-x this weekend which will be the first time really pushing the car since I got it a couple months ago. I expect the gremlins will start to surface at the auto-x event.

If you drive along under constant load (maintaining speed on a flat road in 3rd say) and then tap the gear never into N - does it clunk when it disengages? This is the test the master tech to test as well as it occasionally doing it when going from 2>3 itself.

[JeffB-M3]

Originally Posted by mfurse

If you drive along under constant load (maintaining speed on a flat road in 3rd say) and then tap the gear never into N - does it clunk when it disengages? This is the test the master tech to test as well as it occasionally doing it when going from 2>3 itself.

Thanks for the tip! I tried 3 different things:
1. Cruising at constant speed (25ish mph) in 3rd gear, engage clutch, shift into Neutral: no clunk.
2. Cruising at constant speed (25ish mph) in 3rd gear, take foot off gas, shift into Neutral: very faint clunk. (Aside: in 6th gear at 45mph where was no clunk sound.)
3. Cruising at constant speed (25ish mph) in 3rd gear, keep foot on gas, shift into Neutral: significant clunk. Proved this a couple times...until I started considering how my day would be screwed if I broke my car badly.

Thanks in advance for the help!

[dezzracer]

Originally Posted by CigarPundit

I haven’t heard your car, but I wouldn’t jump to any conclusions. This car makes more NORMAL noises than any car I have ever owned. It clunks, it whines, it clicks. It makes noises when you shut it off. There is a lot of audible stuff going on in this car both during and after operation. By all means, take it to the dealer and have them take a listen, but I’m telling you that this car makes a lot of sounds that other cars don’t seem to make even when everything is perfectly normal.

Ditto in my M3 CS

[Andrew30azs]

Originally Posted by JeffB-M3

I get all sorts of noises from the clutch / transmission area. I sometimes get a clunk like in the video. I also get odd metal-on-metal rattling / grinding when at a low speed and starting to accelerate easily. Sometimes struggle to get the car in 1st gear. Some of the items feel like synchro issues and others I'm still clueless on. The car is still under warranty and have had dealer check for all of them but got the "unable to reproduce" report. I'm doing an auto-x this weekend which will be the first time really pushing the car since I got it a couple months ago. I expect the gremlins will start to surface at the auto-x event.

Did you fix it ? Any update ?

[JeffB-M3]

No, I never sorted anything out. My original post was a short time after getting the car so I think some of it was adjusting how to time clutch releases and some of it is learning the various sounds this car makes. I do still get unexplained noises from time to time which kinda bugs me but I don't sweat it too much.