[meowmer]

Hey everyone, I've been noticing this growling sound that I'm hoping someone can help identify. When I'm traveling at highway speeds (60+ mph) and I release the gas pedal to decelerate, I hear a distinct bass-like growling noise.

Key information:
- Only happens during deceleration from speeds above 60 mph
- Not present when cruising at any speed
- Sound is deep/bassy in nature
- Recently replaced all tires but the issue persists

View post on imgur.com

[aerof16]

How many miles on your car? Hard to tell, does it feel like a vibration resonating through the chassis?

My first guess, with the limited info you provided, maybe you have an engine mount that’s failing.

Pop the hood and have someone floor it and then immediately let off the gas - like pedal to the floor but not to redline, and watch for excessive side to side movement (like a rocking motion). One side will lift under acceleration and then fall once the pedal is released.

You can also shine a flashlight down and look for leaking fluid from the joint if you know what you’re looking at.

[Mosaud1998]

Could be rear differential

[meowmer]

Originally Posted by aerof16

How many miles on your car? Hard to tell, does it feel like a vibration resonating through the chassis?

My first guess, with the limited info you provided, maybe you have an engine mount that’s failing.

Pop the hood and have someone floor it and then immediately let off the gas - like pedal to the floor but not to redline, and watch for excessive side to side movement (like a rocking motion). One side will lift under acceleration and then fall once the pedal is released.

You can also shine a flashlight down and look for leaking fluid from the joint if you know what you’re looking at.

It has 70k miles on it. I don't think it's the engine mount. What else do you think might be the issue?

[meowmer]

Originally Posted by Mosaud1998

Could be rear differential

I was thinking the same. It has 70k miles on it. I don't think the rear diff fluid was ever changed. Do you think changing the fluid would fix the issue?

[Mosaud1998]

Originally Posted by meowmer

I was thinking the same. It has 70k miles on it. I don't think the rear diff fluid was ever changed. Do you think changing the fluid would fix the issue?

I don't think it would hurt

[meowmer]

Originally Posted by Mosaud1998

I don't think it would hurt

Got it. I wasn't able to find anyone facing this issue and I genuinely don't know what to do. First of all, I'll change the diff fluid. What else do you think might be the issue?

[aerof16]

Originally Posted by meowmer

It has 70k miles on it. I don't think it's the engine mount. What else do you think might be the issue?

Did you even check?

It’s nearly impossible to troubleshoot a noise on the internet. I don’t think there’s the slightest chance changing your diff fluid will help with the noise (but it’s good maintenance anyway)unless it’s leaking fluid from a seal and is low, but then I’d expect to it groan all the time.

Either way, you either need to actually troubleshoot the car or pay someone to do it vs just guessing at random things people are saying on the internet.

If you troubleshoot, look around, find some more info to add, we can for sure help, but right now everyone is just guessing because of the lack of data.

[meowmer]

Originally Posted by aerof16

Did you even check?

It’s nearly impossible to troubleshoot a noise on the internet. I don’t think there’s the slightest chance changing your diff fluid will help with the noise (but it’s good maintenance anyway)unless it’s leaking fluid from a seal and is low, but then I’d expect to it groan all the time.

Either way, you either need to actually troubleshoot the car or pay someone to do it vs just guessing at random things people are saying on the internet.

If you troubleshoot, look around, find some more info to add, we can for sure help, but right now everyone is just guessing because of the lack of data.

Yes sir, I did check. And I absolutely understand. I initially searched online to see if anyone else faced this issue but couldn't find any video. Thanks for the suggestion. I think troubleshooting thoroughly is the way to go cuz I don't want to keep driving and make things worse.

[Joe-BMW33]

Flex Disk?

[meowmer]

Originally Posted by Joe-BMW33

Flex Disk?

Noted. Do you think it'd go bad in 70k miles?

[aerof16]

Originally Posted by meowmer

Noted. Do you think it'd go bad in 70k miles?

Yes, they can go bad at that mileage or even lower. It’s an item that BMW should be checking every time they have your car in the shop so, if you do maintenance with them, they should be checking it.

Otherwise, you’d need to get under the car and take a look.

[Joe-BMW33]

Originally Posted by meowmer

Noted. Do you think it'd go bad in 70k miles?

The Flex Disk begins to fracture every ~25k miles for most people. If yours has never been replaced, I am sure it is fractured at 70k. May not be your issue, but probably fractured.

[meowmer]

Originally Posted by Joe-BMW33

The Flex Disk begins to fracture every ~25k miles for most people. If yours has never been replaced, I am sure it is fractured at 70k. May not be your issue, but probably fractured.

Got it. Thanks. Is it easy to install?

[meowmer]

Originally Posted by aerof16

Yes, they can go bad at that mileage or even lower. It’s an item that BMW should be checking every time they have your car in the shop so, if you do maintenance with them, they should be checking it.

Otherwise, you’d need to get under the car and take a look.

Thank you so much. I'm not sure if this was ever replaced as I just got the car.

[CMK]

Originally Posted by meowmer

Got it. Thanks. Is it easy to install?

FBO with what you need, as always:

https://g30.bimmerpost.com/forums/sh....php?t=1985849

[Joe-BMW33]

Originally Posted by meowmer

Got it. Thanks. Is it easy to install?

Google or search here, plenty of information on Flex Disk. I don't mind holding your hand, but honestly, there are threads and threads on this.

[meowmer]

Originally Posted by Joe-BMW33

Google or search here, plenty of information on Flex Disk. I don't mind holding your hand, but honestly, there are threads and threads on this.

Thank you!

[meowmer]

Originally Posted by aerof16

How many miles on your car? Hard to tell, does it feel like a vibration resonating through the chassis?

My first guess, with the limited info you provided, maybe you have an engine mount that’s failing.

Pop the hood and have someone floor it and then immediately let off the gas - like pedal to the floor but not to redline, and watch for excessive side to side movement (like a rocking motion). One side will lift under acceleration and then fall once the pedal is released.

You can also shine a flashlight down and look for leaking fluid from the joint if you know what you’re looking at.

I took a video again. What do you think about this?

View post on imgur.com

[ezaircon4jc]

Originally Posted by meowmer

I took a video again. What do you think about this?

View post on imgur.com

I'm no mechanic, but that looks normal to me.

[aerof16]

Originally Posted by meowmer

I took a video again. What do you think about this?

https://imgur.com/a/ghnVF2z

The movement doesn’t look too excessive, so the only other thing to do is check and make sure the mounts aren’t leaking. They are hydraulically filled, so the first sign of failure on them is leakage and then the mount collapses. If not fixed, then they break down further and that’s where you see more movement.

I’m not trying to convince you that they’re bad - just the first thing I’d check based on what you described.

[meowmer]

Originally Posted by aerof16

The movement doesn’t look too excessive, so the only other thing to do is check and make sure the mounts aren’t leaking. They are hydraulically filled, so the first sign of failure on them is leakage and then the mount collapses. If not fixed, then they break down further and that’s where you see more movement.

I’m not trying to convince you that they’re bad - just the first thing I’d check based on what you described.

Got it. Thank you so much!