Deceleration sound

[dg_moore]

I have a 2010 3.8. When I lift my foot from the accelerator at speeds above about 50 mph I hear a droning or "moaning" sound a little bit like the sound of a louder-than-stock muffler. If I apply a little bit of accelerator and bring the rpm's up to match the transmission (basically coasting under no load) the sound disappears.

I don't think this is exhaust noise because the mufflers just aren't that loud, and there is no noticeable noise when accelerating.

Has anybody else experienced this?

 

[MichaelOne]

Are you in Drive, or perhaps using the manu-matic when this happens?

 

[dg_moore]

In Drive

 

[nearwater]

Weird.
American V8s with aftermarket exhaust makes burbling, popping sound when the car's in gear and is decelerating, but never heard anything similar on a sedan w/ quiet exhausts.
You think it's drivetrain related?

Dan

 

[CanukV6]

I have a 2010 3.8. When I lift my foot from the accelerator at speeds above about 50 mph I hear a droning or "moaning" sound a little bit like the sound of a louder-than-stock muffler. If I apply a little bit of accelerator and bring the rpm's up to match the transmission (basically coasting under no load) the sound disappears.

I don't think this is exhaust noise because the mufflers just aren't that loud, and there is no noticeable noise when accelerating.

Has anybody else experienced this?

I have the same sound and the cause is the Differential. Mine is more of a whine than a moan, but it is most noticable at 50mph when coasting. Any slight application of the throttle and the noise disappears. I have had this since day one and it hasn't got any worse.

 

[dg_moore]

I have the same sound and the cause is the Differential. Mine is more of a whine than a moan, but it is most noticable at 50mph when coasting. Any slight application of the throttle and the noise disappears. I have had this since day one and it hasn't got any worse.

That's interesting. I wonder if this is within normal limits or if something's out of whack. Did you determine yourself that this is differential related, or did you learn from another source?

 

[CanukV6]

In my car it is definitely coming from the Diff and I have had this since day one. I have heard this same noise from some older cars with RWD although I have to say I wasn't expecting to hear it from a new car. I mentioned it to my dealer when I took it in for service and he noted it down and said if it gets worse they would talk to Hyundai. It hasn't got any worse and since I only really hear it on the overrun (coasting) and specifically at around 50mph, it is not such a big deal.

 

[nearwater]

Is the diff different on V6 vs V8?
I don't think I'm experiencing this on my V8.

Dan

 

[CanukV6]

The V8 has a Limited Slip Diff, so yes it is different.

 

[dave3.8]

Try swapping out the dif oil for synthetic - most of the sound goes away.

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[dg_moore]

Try swapping out the dif oil for synthetic - most of the sound goes away.

Really? Wonder why that would be...

 

[nearwater]

Really? Wonder why that would be...

Forum members of my previous cars switched out the diff oil and added GM friction modifier.
Lots of times it solved the noise problem.

Dan

 

[Mark_888]

Don't do anything yourself yet. I am fairly certain (depending on your build date) that there is a TSB that covers this problem for some 2009 Genesis sedans. I have posted the details of the TSB before in other threads, but don't have the specifics available to me right now (you can try the search engine). The TSB involves removing the axle and inserting a spacer to fix the problem. Obviously, all under warranty.

The TSB covers both the 2009 V6 and V8, but the build dates are different since they made the factory change mid-model-year on the V8 before the V6 (If I recall correctly, or maybe the other way around) until they realized that both are affected.

My build date is covered by the TSB, but so far I have not heard the noise.

 

[dg_moore]

I have a 2010 3.8. When I lift my foot from the accelerator at speeds above about 50 mph I hear a droning or "moaning" sound a little bit like the sound of a louder-than-stock muffler. If I apply a little bit of accelerator and bring the rpm's up to match the transmission (basically coasting under no load) the sound disappears.

I don't think this is exhaust noise because the mufflers just aren't that loud, and there is no noticeable noise when accelerating.

Has anybody else experienced this?

I took the car in for initial scheduled maintenance this morning. The tech verified the noise and said he had never observed it before. He called Hyundai and they advised him that the transmission needs to be replaced.

The dealer is getting the unit and will provide me a loaner while they do the repair. He assured me that the car is safe to drive until then. I didn't ask if there is a service bulletin on this, but I will when they call me back.

 

[nearwater]

He called Hyundai and they advised him that the transmission needs to be replaced.

That's a costly repair for Hyundai. Let us know how it goes.

Thanks,

Dan

 

[dg_moore]

I took the car in for initial scheduled maintenance this morning. The tech verified the noise and said he had never observed it before. He called Hyundai and they advised him that the transmission needs to be replaced.

The dealer is getting the unit and will provide me a loaner while they do the repair. He assured me that the car is safe to drive until then. I didn't ask if there is a service bulletin on this, but I will when they call me back.

The car goes in for a transmission transplant tomorrow. I'll report back when I get the diagnosis of what actually went wrong with the original.

 

[dg_moore]

The car goes in for a transmission transplant tomorrow. I'll report back when I get the diagnosis of what actually went wrong with the original.

Dropped the car this morning; got a loaner and went to work. At 3:30 they called me and said the car was ready. Picked it up and the problem is fixed. There was no TSB on this problem, and the service manager said Hyundai would not know exactly what the problem was until their engineers disassemble the transmission. I asked him to let me know if/when Hyundai figures out what went bad. In the meanwhile, a good service experience with minimum inconvenience.

 

[dg_moore]

The dealer replaced the transmission a few weeks ago - the sound is less noticeable, but it's still there. I'm due for service in a couple of weeks - will have them take another look. I'll also mention the differential lubricant issue.

 

[dg_moore]

Well, Hyundai replaced my transmission a few months ago, and the deceleration sound was greatly reduced but not eliminated. Now, however, it has increased back to the original level (before the transmission replacement). The car goes in tomorrow for 7500 mile service and they are going to revisit the sound problem. I'm going to tell them about the synthetic differential oil and the possible axle spacer TSB that were mentioned previously in this thread. I hope they get this figured out - will report back what the results are.

 

[dg_moore]

OK - just heard from service dept. They called Hyundai (again) and learned that Hyundai has a case open for this problem - apparently there are several owners with this problem. They do not know what is causing it, but are working on it. They assure me that it is not a safety issue, and that nothing is broken or likely to break. They are to notify me when a solution is found. So I guess I'll just have to live with it for a while - it's not a big deal, it's just that the sound is not normal.