Deep Bass Noise

[LV392]

Hey everyone,
I have a 392 with 3k miles on it. Just recently the jeep has been making an intermittent noise that is driving me crazy. When driving (not parked), the car will randomly make a deafening deep bass noise. The sound occurs when moving, doesn't matter if you are accelerating or coasting. It sounds like a car with a massive subwoofer is right next to you. The performance exhaust is turned off and the sound is louder than the performance exhaust. It is loud enough that it is nearly unbearable. I'll take it to the dealer but was just hoping someone could point me in the right direction.
Thanks!

 

[YukonCornelius]

Welcome @LV392 ! And congrats on the new ride!

Question: do you notice it on the outside (ie., have someone drive by while your outside the vehicle)?
Does it get louder with speed at all or is it constant?

 

[LV392]

I'll have someone drive by and see if I can hear it. Could be hard because of the intermittent nature of the sound. As for volume, it seems to have to levels that are not dependent on speed. The levels are loud and super loud but there is no in between.

 

[YukonCornelius]

Let us know... could just be the noise of the drivetrain, or a shoddy joint in the exhaust somewhere - which given the sort-of non existant sound deadening, would certainly drone but you'd more than likely be able to tell immediately if it were either of those.

The one oddball that could possibly be the culprit: they do have active noise cancellation tech - and that would be a low frequency, almost bassy sound if it were audible. Maybe it's glitching?

 

[HearHear]

I have something like that too with only 1,000 miles on it. I dare say it’s normal. Sounds like full open exhaust for a few seconds at lower speed for me. My guess? Random variable cylinder activation (all cylinders activated) mixed with full open exhaust. I have no idea what I just typed so don’t believe me. But it sounded right and in all seriousness doesn’t bother me. It just sounds like the beast under the hood is getting aroused.

 

[Guest862]

I believe they call this the “exhaust drone”

 

[veddersbetter]

I have something like that too with only 1,000 miles on it. I dare say it’s normal. Sounds like full open exhaust for a few seconds at lower speed for me. My guess? Random variable cylinder activation (all cylinders activated) mixed with full open exhaust. I have no idea what I just typed so don’t believe me. But it sounded right and in all seriousness doesn’t bother me. It just sounds like the beast under the hood is getting aroused.

I notice the MDS makes the exhaust sound different.. maybe a little deeper... and kinda shitty. I wish there was a way to shut if off around town and turn it back on while cruising on the highway. It is the one complaint I have of the 392.

 

[Idaho392]

That terrible sound is a combination of the vehicle going into V4 mode, and the active noise cancellation trying to compensate for the change in exhaust note. There are only two options:

(1) have a PCM tune installed like the Livernois one. It will disable the V4 mode and thus stop that noise. This was my personal solution about 5 months ago. It's great.

(2) Disconnect the Alpine subwoofer in the cargo area. You lose all your deep bass from the stereo, but that will stop the ANC system (as it all goes thru the subwoofer only).

 

[Jeepstin392]

It‘s the exhaust drone when MDS engages.

 

[David]

That terrible sound is a combination of the vehicle going into V4 mode, and the active noise cancellation trying to compensate for the change in exhaust note. There are only two options:

(1) have a PCM tune installed like the Livernois one. It will disable the V4 mode and thus stop that noise. This was my personal solution about 5 months ago. It's great.

(2) Disconnect the Alpine subwoofer in the cargo area. You lose all your deep bass from the stereo, but that will stop the ANC system (as it all goes thru the subwoofer only).

I’ve read your post over and over while trying to solve this problem. I’ve unplugged anc but it seems to do nothing. I’m considering the Livernois tune. Did you work with your Jeep dealer on it or just say F$&! It and solve it for yourself? I would really like to hear your thoughts on the tune.

 

[Framinal]

Does the XR model go into v4 mode? I haven't seen anything that would indicate it.

 

[Robr651]

Does the XR model go into v4 mode? I haven't seen anything that would indicate it.

Yes same engine

 

[Framinal]

Ok so where will it tell me it's in v4 mode? I have yet to see any notification anywhere. Thx

 

[Robr651]

Look at you center cluster in the dash it’ll occasionally pop up. The 6.4 has MDS

 

[Robr651]

You’ll notice it mostly on light acceleration just cruising around. It might be less noticeable with the XR gearing. Another XR owner can chime in, but we all have MDS (both XR and non-XR)

 

[Jeepstin392]

Put on the MPG screen. Light throttle while cruising, it will engage.

 

[Guest862]

If driving in the tiptronic shift mode where you flip the shifter to the left does it still activate this 4 cyl?
I keep her screaming most of the time but I have definitely noticed the noise in automatic

 

[Jeepstin392]

If driving in the tiptronic shift mode where you flip the shifter to the left does it still activate this 4 cyl?
I keep her screaming most of the time but I have definitely noticed the noise in automatic

IDK. I think I recall seeing it engage in manual mode while cruising, but can’t recall fir certain.
It seems reduced with the Borja exhaust. I did notice that.

 

[Robr651]

Nice article on how it works:

What Is Hemi MDS?

We explain how Chrysler Hemi MDS cylinder deactivation works, what goes wrong, and how to fix it when it breaks.

www.motortrend.com

 

[David]

Great news - found a simple plug and play fix - https://lljcustoms.com/products/2018-2022-jeep-dodge-ram-llj-anc-bypass?_pos=1&_sid=6d46def15&_ss=r