Whirring Noise - Rear Differential?

[Nermel]

Hey All -

I have a 2001 V70 XC with approx 110k. Its in great shape, and has been fantastic for the year or so that I've owned it. But recently, I've been hearing a loud oscillating 'whirring' noise.

It becomes noticable at around 40mph, and gets louder and faster in the oscillation till about 50mph, then subsides and gets quieter at highway speeds. It doesnt seem to have anything to do with the transmission as it happens in both drive and neutral.

I'm guessing this may be my rear differential drying out and maybe needing to be flushed/checked? Anyone have other ideas?

I'm on a fairly tight budget... So hopefully it won't be too bad to fix.

Thanks for any insight!

[Astro14]

If its from the back...more likely are the wheel bearings....you sure of the location?

[Nermel]

If its from the back...more likely are the wheel bearings....you sure of the location?

Thanks Astro - I'm not, haven't really been able to tell where exactly its coming from. I can feel the reverberations/oscillations in the steering wheel and gas pedal however.

If it is wheel bearings, is that something I should fix sooner than later? Could I be doing damage control if I were to take it in right away? Any idea of a cost for replacement?

Thanks again!

[jkochis]

Sounds like wheel bearings. I left mine for like 30k or more until they really got loud. It was even causing a vibration in the gas pedal.

[Willy]

It sounds like a wheel bearing. But tires can make the same noise when cupped or scalloped.
This happened to me last year, albeit on the front side of the car.
You may try to swap front and rear tires to see if the noise stays or moves to the front.
The rear differential is easily checked for fluid level. Remove the fill plug,
fluid level should not be very much below the bottom of the fill hole. Volvo uses long life fluids
that don't have to be replaced. I think it is still a good idea to consider doing just that.
Willy

[Nermel]

Hi all, thanks for the info so far. After getting a second/passenger opinion, it seems that the noise is coming from the front end of the vehicle. I did check the differential fuel level, which looks to be just fine.

Does this change anyone's opinion? The tires are due to be replaced some time this summer, but it does seem quite loud to just be the tires.

Again, thanks Volvo gurus for any input!

[coflynn]

A pretty easy test: when the car is at a speed making the noise, turn the car so that it banks slightly. This will put more of the cars weight on one wheel than the other. If the noise noticeably changes there is a good chance it's the wheel bearings - based on when the noise increases you can also narrow down which wheel. As mentioned it's worth trying to swap tires to eliminate that though, as the tires could also be making that noise, which would also change depending on pressure applied.

If you wish to DIY I had posted a guide for my S60 which should be roughly the same at http://www.volvo-forums.com/t27042-2002-s60-awd-wheel-bearing--ball-joint-replacement.htm

While I don't think you'll do damage by riding it out for a while, you might as well replace now. If the original ones lasted 110k, do you really care about trying to save another 20k? This way you can perform the maintenance on your terms (e.g.: choose a convenient day, pick your fav dealer or DIY, etc).