Whining - front or rear?

PVSPete · Feb 22nd, 2021, 21:35

I've posted before regarding a whining noise from the drive train of my 2005 D5 XC90 auto. 140,000 miles and a few people said they'd got similar. The noise isn't there for the first few miles from cold, but then starts and is most noticable around 40mph on a light throttle. When the throttle is backed off, the noise stops. Open the throttle a little, it comes back. I've recently found a post from cpu_man who describes just this. His was ultimately put down to a failed pinion bearing in the rear differential.
I had previously found that the front angle gear / bevel gear unit had very rusty looking oil in it and despite changing the oil 3 times I felt it was probably the source of my noise . . . so I located a replacement used angle angle assembly from a crashed car and last week fitted it. The noise may be less pronounced, but is still there.
So I'm back to ask what you think?
Is the secondhand front angle gear a bad one?
Do I have a failing rear diff? Or Haldex?
Is there a test to help decide where the fault is?
Is there a wireless microphone you can connect to a phone app to help locate the source of the noise?
Any thoughts appreciated.

Feb 22nd, 2021, 21:35	#1
PVSPete Junior Member Last Online: Jan 5th, 2024 15:14 Join Date: Nov 2019 Location: Peterborough	Whining - front or rear? I've posted before regarding a whining noise from the drive train of my 2005 D5 XC90 auto. 140,000 miles and a few people said they'd got similar. The noise isn't there for the first few miles from cold, but then starts and is most noticable around 40mph on a light throttle. When the throttle is backed off, the noise stops. Open the throttle a little, it comes back. I've recently found a post from cpu_man who describes just this. His was ultimately put down to a failed pinion bearing in the rear differential. I had previously found that the front angle gear / bevel gear unit had very rusty looking oil in it and despite changing the oil 3 times I felt it was probably the source of my noise . . . so I located a replacement used angle angle assembly from a crashed car and last week fitted it. The noise may be less pronounced, but is still there. So I'm back to ask what you think? Is the secondhand front angle gear a bad one? Do I have a failing rear diff? Or Haldex? Is there a test to help decide where the fault is? Is there a wireless microphone you can connect to a phone app to help locate the source of the noise? Any thoughts appreciated.

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