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  #1  
Old 11-09-2011, 08:34 AM
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Growling and humming from the rear

My first guess is another wheel bearing but I wanted to see if there is another possibility. The only reason I am wondering is the strange behavior of the noises. At 40ish MPH the sound is kind of a growling/moaning noise and is strongest when coasting down a hill. At 70ish MPH the noise is a high pitch hum. What is most strange is that the hum fades in and out on a regular period. It is almost like the beating you get when you pluck two strings of a guitar that are supposed to be the same note but are slightly off from each other.

So is the bearing still the #1 suspect or can it be something else?
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  #2  
Old 11-09-2011, 05:06 PM
92snowmachine 92snowmachine is offline
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Re: Growling and humming from the rear

if it's not your wheel bearing it could be your rear diff or your rear axle is out of balance.
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  #3  
Old 11-10-2011, 05:44 AM
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Re: Growling and humming from the rear

Anyone else have any comments on this?
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1996 Polo Green Subaru SVX LSi, 168,XXX miles, Redline D4 ATF, Redline 75W90 gear oil, K&N HP-4001 Oil Filter, Mobil 1 5W50 FS (3qt) and 5W30 High Mileage (4qt) Oil Blend, Motul RBF600 Brake Fluid, AC Delco A975C Air Filter, NGK BKR6EIX-11 plugs, Centric Rotors, Power Stop Evolution Carbon Fiber Ceramic Brake Pads
2005 Gray Acura RL, 165,XXX miles, Redline D4 ATF with Lubegard Platinum Protectant, Mobil 1 5W20 High Mileage Extended Performance Oil
2009 Red Toyota Venza, 123,XXX, Mobil 1 5W30 High Mileage Oil
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Old 11-10-2011, 06:08 AM
Tapani Tapani is offline
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Re: Growling and humming from the rear

My open R160 4.444 rear diff is on its way out...... sound familiar

Tapani
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  #5  
Old 11-10-2011, 07:07 AM
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Re: Growling and humming from the rear

I had a bad rear diff that was making noise that got louder with speed and it had a vibration that could be felt. When that happened I could distinguish that it was not a wheel bearing but I was not entirely sure.
I would have a shop check them on a lift, they can listen with a scope while someone brings it up to speed while on the lift. Should be quick for them to diagnose.
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Last edited by Sean486; 11-10-2011 at 07:28 AM.
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  #6  
Old 11-10-2011, 07:22 AM
DeltaSlyHoney DeltaSlyHoney is offline
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Re: Growling and humming from the rear

My RR bearing went recently. Sounded a lot like what you describe.
If you can get someone else to drive and sit in back you should be able to hear if its coming from one side or the other. Thats what I did anyhoo.
I'm guessing if it's the diff youd get an even tone sitting in the middle and a pleasant rumble in the jockeys.
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Old 11-10-2011, 08:02 AM
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Re: Growling and humming from the rear

Yeah, I am not getting any noticable vibrations. And it sounds like the noise is coming primarily from the right side but I could be wrong on that. There are other noises, like a faint very high pitched whistle or whine that seems centered but it is unrelated as far as I could tell.
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1996 Polo Green Subaru SVX LSi, 168,XXX miles, Redline D4 ATF, Redline 75W90 gear oil, K&N HP-4001 Oil Filter, Mobil 1 5W50 FS (3qt) and 5W30 High Mileage (4qt) Oil Blend, Motul RBF600 Brake Fluid, AC Delco A975C Air Filter, NGK BKR6EIX-11 plugs, Centric Rotors, Power Stop Evolution Carbon Fiber Ceramic Brake Pads
2005 Gray Acura RL, 165,XXX miles, Redline D4 ATF with Lubegard Platinum Protectant, Mobil 1 5W20 High Mileage Extended Performance Oil
2009 Red Toyota Venza, 123,XXX, Mobil 1 5W30 High Mileage Oil
1992 Red Ferrari 348 ts, 82,XXX, Redline everything
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  #8  
Old 11-10-2011, 09:05 AM
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Re: Growling and humming from the rear

Driving it on a lift and listening with a mechanic's stethoscope to the different possible points will narrow it down really quick.

The really bad wheel bearing on my blue car was actually enough to cause a wobbly/vibratey feeling. For a while I actually thought I had a bad axle because of it. But it was extremely bad, and had been bad for a very long time too:

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  #9  
Old 11-10-2011, 10:21 AM
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Re: Growling and humming from the rear

Quote:
Originally Posted by icingdeath88 View Post
Driving it on a lift and listening with a mechanic's stethoscope to the different possible points will narrow it down really quick.

The really bad wheel bearing on my blue car was actually enough to cause a wobbly/vibratey feeling. For a while I actually thought I had a bad axle because of it. But it was extremely bad, and had been bad for a very long time too:



THE EVIL WHEEL BEARING RETURNS!!! KILL IT WITH FIRE.
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  #10  
Old 11-11-2011, 05:49 AM
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Re: Growling and humming from the rear

Wheel bearing(s) gets my vote. I suppose rear differentials do fail, but consider the odds.

I noticed when I had a front wheel bearing going bad that the sound varied depending on how the suspension was loaded. Sometimes I couldn't hear it at all. Other times I just turned-up the stereo.

dcb
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  #11  
Old 11-11-2011, 03:09 PM
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Re: Growling and humming from the rear

Quote:
Originally Posted by dcarrb View Post
Wheel bearing(s) gets my vote. I suppose rear differentials do fail, but consider the odds.

I noticed when I had a front wheel bearing going bad that the sound varied depending on how the suspension was loaded. Sometimes I couldn't hear it at all. Other times I just turned-up the stereo.

dcb
The mechanic agrees. I ordered a Timken bearing from autoparts123.com and will have it installed on Thursday. How easy is it to remove the sway bar bushings once the car is up on a lift? I am thinking of asking him to grease up the bushings and re-install them while he has the car up. The reason is that I read one person's experience of having their sway bar shift to one side and cause a rattling noise. Presumably it shifted and stuck.
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1996 Polo Green Subaru SVX LSi, 168,XXX miles, Redline D4 ATF, Redline 75W90 gear oil, K&N HP-4001 Oil Filter, Mobil 1 5W50 FS (3qt) and 5W30 High Mileage (4qt) Oil Blend, Motul RBF600 Brake Fluid, AC Delco A975C Air Filter, NGK BKR6EIX-11 plugs, Centric Rotors, Power Stop Evolution Carbon Fiber Ceramic Brake Pads
2005 Gray Acura RL, 165,XXX miles, Redline D4 ATF with Lubegard Platinum Protectant, Mobil 1 5W20 High Mileage Extended Performance Oil
2009 Red Toyota Venza, 123,XXX, Mobil 1 5W30 High Mileage Oil
1992 Red Ferrari 348 ts, 82,XXX, Redline everything
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  #12  
Old 11-11-2011, 04:04 PM
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Re: Growling and humming from the rear

Please have them check the hub. I'm replacing my bearing again after less than 10,000 miles because of a worn hub.
Gene
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  #13  
Old 11-12-2011, 08:14 AM
dcarrb dcarrb is offline
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Re: Growling and humming from the rear

The sway bar bushings shouldn't be a big deal. Be sure they're not cracked. Oil-soaked front bushings should be replaced. Seems more likely that a rattle from a sway bar would be due to bearing deterioration. I know from experience that having one split apart and fall out results in an awful racket.

dcb
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