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Discussion Starter · #1 ·
I recently bought an '07 XC90 with V8. It needed tires when I bought it and had some noise that I thought (hoped?) would be tire noise due to the worn tires. I just had new tires put on and some of the noise is gone, but there's still a whine or howl type noise between about 45-60mph. It seems much worse on deceleration than acceleration. I'm not quite sure if it's coming from the front or rear of the vehicle as it seems to resonate all through it. I took a video of it, trying to capture the sound - but it didn't come through very well.

When driving 30 or 70, you don't hear it.

What should I check? Or, just replace fluid in differentials and see if it helps?

I'll try to capture the sound again and post it.
 

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Initial things to inspect would be 1) wheel bearings and 2) the joints on the front and rear (particularly the front) of the prop shaft that runs the length of the car just above the exhaust. The front joint is subject to a lot of exhaust heat. It can be rebuilt, or you can replace the whole shaft, including joints.
 

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I would absolutely check wheel bearings also. You can gauge that by (safely) swerving the car left or right at speed. If it changes pitch or goes away as one side of the car becomes unloaded then you know it's a bearing.
 

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Discussion Starter · #4 ·
I would absolutely check wheel bearings also. You can gauge that by (safely) swerving the car left or right at speed. If it changes pitch or goes away as one side of the car becomes unloaded then you know it's a bearing.
First, there was also a rattle sound at certain RPMs, which I found the front muffler 'skin' rusting off. It seems there is a coating of something over the front muffler that has separated and was rattling against the heat shield and the driveshaft going to the rear. I put some coat hangers around that temporarily to pull the 'skin' back down and keep it tight to the muffler, away from the heat shield.

Back to the whine/howl sound: I tried the swerving method to check the wheel bearings. The sound didn't change a bit. It seems like the sound is coming from the rear of the vehicle. The driveshaft does have some play when I was under there tightening down the 'skin' of the muffler. I rotated it back and forth to see how much play there was. It seems like it's about 3/8" or so of free play. Is this where I should pay attention? Any testing or checking that can be done to make sure it's the cause of the noise before I start replacing parts?
 

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so, above the muffler, there is a bearing for that drive shaft, i think that would be the only place you would get a "whine" from there. There have also been some reports of whining coming from the rear differential. I haven't done much research on that because (knock on wood) I haven't had to, but it's worth checking out.
 

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Angle gear. Had the same problem on my S60R. You can't judge where the sound is coming from because it's right underneath you, basically.
 

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Whine on deceleration is an almost-certain sign of a differential issue. Which in this car translates to angle gear, or rear diff. There's a front diff, but it's internal to the transmission, and a very rare problem here.
 

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Discussion Starter · #8 ·
I haven't taken anything apart yet, but have a little more info from my 'test results' -

While the noise is loudest mainly on deceleration from 60mph down to 40mph, it is noticeable down to about 10mph. If I accelerate during that 60-40 range, there's a brief different, louder howl while I'm pressing on the accelerator and then most of the howling stops. This is repeatable every time I do it.

Swerving side to side with the steering wheel makes no change in the sound.

I have not yet tried putting it in neutral from 60-40mph to see if the sound is still there, but will try that tonight.

I bought new Pirelli Scorpion tires recently and the outsides of the front tires seem to be wearing a little more than the rest of the tire - and definitely more than the rears. I'm not sure if it's out of the ordinary wear though. My wife drives the vehicle and I'm pretty sure she's not taking fast corners or driving it hard.

I'll reply back after testing for the noise after putting it in neutral.
 

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While the noise is loudest mainly on deceleration from 60mph down to 40mph, it is noticeable down to about 10mph. If I accelerate during that 60-40 range, there's a brief different, louder howl while I'm pressing on the accelerator and then most of the howling stops. This is repeatable every time I do it.
Hate to say it but it sounds a lot like the angle gear. Interested to hear the results from the neutral test.

Do you have any inkling where the noise is emanating from, front or rear?
 

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I can tell you that when you replace the front muffler I would go for an oem replacement. I did mine on the cheap after the outer casing peeled off, and it created a couple of problems. The front factory muffler is oval for a reason. I replaced it with a round Walker resonator (they couldn't get any oval ones of similar size) but with movement of the suspension the drive shaft would occasionally lightly touch it and it would schreek like a seized bearing. A couple bashes of a hammer on the muffler fixed that.
But later when its time to replace the rear muffler and you don't want to spend $1600+ for one, the oem front will allow you some options. You can either delete the rear muffler completely, if you don't mind a little bit extra growl, or add a small aftermarket muffler.
The rear muffler doesn't do much muffling at all compared to the front, especially considering the cost differences. I'm still running the Walker front with a small stainless rear and while it sounds great revving it up sitting still, I find it drones too much when under load.
 

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If putting it into neutral makes the whine go away, is it indicative of a failed angle gear?
Not necessarily. It just gives more information. For example, if the whine *doesn't* go away, it might indicate a tire, wheel bearing or other non-driven element. All these sources can be really hard to pinpoint so the more info the better.
 

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Ok good to know, especially since the previous owner replaced the angle gear last July. I'm experiencing a whine as well but it sounds more like it's coming from the front. I was also told I need a new left front driveshaft, not sure if that is contributing. The moose has a date with our dealer this week, so we'll see what they have to say.
 

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That is close to $1700 in labor! A new remanufactured pump is under 200 and a tensioner is a lot less than that. Where are you taking it?

Sent from my SM-G900R4 using Tapatalk
 

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Parts are $760 from Tasca:

Belt Tensioner - 200
Idler - 50
Belt - 44
Pump - 444
O-ring - 6
Fluid - 18

Labor is the balance at ~9 hours @ $130/hr.

This is at the local dealer, which is pretty reputable - Don Beyer in Falls Church, VA. My indy shop is ~115/hr and they get really annoyed when I bring my own parts and don't provide a loaner car and won't give me a ride to my office because it is .5 miles outside of their radius...
 

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Dealer work. Got it. Well, it will most likely be done right. It does appear to be a long job. Once done that V8 should last you a long time.

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The 2.5t job appears simple & DIY easy. I am not familiar with the pump location on the V8. Judging by labor cost it must be behind/under the engine. Cool that the parts are warranted for life!!

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Discussion Starter · #20 ·
I did check the noise on mine while decelerating in neutral....there is NO change in the noise at all. Exactly the same whether in neutral and decelerating or in drive and decelerating.

I'll look into replacing the angle gear then, since so many suggested that is the problem making the howling noise.

I'm a DIY guy, so if possible I'll give that a go myself.
 
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