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High pitched whine at freeway speeds


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All,

 

I'm trying to diagnose a high-pitched whining noise I get at freeway speeds. Has been happening for a couple of weeks.

 

Starts at about 40mph and sounds something between a whistle/whine and metal-on-metal contact, although it seems to have a resonant quality to it, like it hits a point where the noise becomes disproportionately louder because of frequency. The sound cannot be traced by ear to a wheel or the trans - just sounds like it is coming from all around the car. It's loud too, like I can hear it over the stereo easily.

 

I suspected a wheel bearing so I checked and found the front right bearing was a little loose. Installed a new Subaru bearing and the noise is largely unchanged.

 

Sounds kinda like the dust shield is making light contact, but I checked that.

 

I also recently put my winter tires on. Can't tell if that happened before or after the noise as the noise has been growing over the last couple of weeks.

 

 

While driving, the noise is entirely dependent on road speed. The sound does not change with acceleration/deceleration, gear changes, or putting the 5spd into neutral and revving. It does not change with steering, lane changes etc.

 

Opening or closing windows does affect the noise, nor does it help locate the noise (the sound of air rushing is louder than the noise, so I can't "hear the noise through the open window")

 

 

I've been searching for a couple of days, and this is the best I can can come up with for a shortlist of potential culprits:

 

- Other front wheel bearing. Don't think it's this because that bearing is solid.

- Center diff bearings. Don't think it's this because folks have described the noise changing with acceleration/deceleration.

- Center carrier bearing. Potentially, but can't find much on the symptoms for this.

- New tire noise. I've had these tires through a couple of winter seasons and this noise it new.

- Yakima roof rack whistling. Other than putting some tinsel garland on the roof rack a couple of weeks ago (!) I can't see this creating the noise. Still, I have just removed the roof rack and will see if the noise has gone away when I drive home tonight.

- Brake dust shield contacting rotor. I had a scraping noise when turning right on left front after putting the winter tires on, so I bent the shield back a little and that fixed it. That sound was at low speed though, so a different kind of sound altogether.

- Window whistling / gusset seal. I'm familiar with this after having replaced the seal on two different cars. The sound is very different, and that sound would be 'solved' by pressing on the window - this sound is not.

 

Anyone else got an ideas? :confused:

Edited by Scruit
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Are you sure it's not just the winter tires? I also noticed a quite-pronounced high-pitch road noise at higher speeds since I swapped to my winters, though I think it's mostly there when I'm cornering (on-ramps and such). I'm running Michelin X-Ice 3 for tires. I can't say I noticed this noise the previous two winters, but until this winter I always had music playing.
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I'm 99% sure it's not the winter tires. The noise has been getting worse, and the last two days has been really loud. The tires have been on since Thanksgiving.

 

I'll try to get an audio recording if the noise is still happening on my way home. Also, because I love tools, I'll grab a set of chassis ears to help troubleshoot.

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Have you checked your turbo lately? I was getting a whine for a week or 2 before my TD04 seized on my Forester, mostly at startup but I could hear other times as well.

 

Pull the TMIC to see if there is oil in it.

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"Simple incompetence is a far more sinister force in the world than evil intent."

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My turbo has 18k on it, the whole engine was rebuilt a couple of years ago. The whine is dependent on road speed, and the sound does not change even if I push the clutch in and allow the engine to drop to idle while doing 70mph.

 

Thanks for the suggestion.

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The whine has evolved.

 

First, removing the roof rack (with christmassy tinsel garland!) resulted in the overall sound profile changing a little. The roof rack was causing an unrelated whistling (not unexpected) and was making it difficult to figure out the direction of the sound. Now that is gone it is easier to pinpoint.

 

Now it sounds like the high-pitched sound component from a jet engine, and comes from directly under the shifter. I suspect the center diff bearings.

 

I'll throw my chassis ears on it to confirm before I buy the parts, but I am expecting to have to rebuild the center differential.

 

Luckily I have alternate transportation for the next week or two while I wait for parts.

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Chassis ears confirmed the center diff sounded like an altoids tin full of marbles.

 

Took an hour to get it torn down to a point when I'm about the pull the diff housing off - and the diagnosis appears to be confirmed - the output shaft has a ton of lateral play.

 

Waiting for parts to arrive, then I'll get the diff rebuilt and put back together.

 

Got an hour in it so far, and have the exhaust, heat shield, propshaft, crossmember and shifter linkage removed.

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Sorry, I wasn't clear. I mean I'll replace all 4 bearings in the extension housing in my shop here. I'll evaluate the actual diff itself while its out, I wanted an opportunity to at least check out the diff before committing to the $500 spend.
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Well, fingers crossed I don't have the split the case and it's just bearings in the extension housing. I've already decided that a bad trans = new car* for me. Just not worth the time and money any more.

 

* That Tesla 3 looks pretty nice...

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I did center diff bearings about 70k miles ago. I drove with them making noise until it started getting louder (for at least 20k miles) and I was able to figure out what it was and swapped the bearings myself. Since you are changing them now, you'll probably be fine.

 

+1 on the any-mechanical failure to the engine or trans and I'm going electric bandwagon.

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+1 on the any-mechanical failure to the engine or trans and I'm going electric bandwagon.

 

Have you seen the new Leaf for 2018? They're doing a much better job of styling it like a "car" rather than an "electric car"... I'd keep the LGT, but as a project car, not a DD. Free me up to do some more extreme stuff like 6spd etc.

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I did center diff bearings about 70k miles ago. I drove with them making noise until it started getting louder (for at least 20k miles) and I was able to figure out what it was and swapped the bearings myself. Since you are changing them now, you'll probably be fine.

 

 

Finger crossed. The parts just arrived today so the work will be this weekend (starting on the assumption that I'm not replacing the center diff itself, just the bearings and seals/gaskets etc) Fingers crossed...

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  • 4 years later...

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