For that past 6-8 weeks there has been a resonant vibrating noise (lower frequency sound that can sound like a rapid knocking at worst) at 60mph+, which tends to go if I take my foot of the gas, on our 2004 Subaru Forester. The dealer had the car for 3 days and could not find the problem, even after replacing a worn wheel bearing, swapping out both front axles, rotating the tyres and removing roof bars. Now a friend has suggested it could be a wheel alignment problem. I intend to call the dealer back to ask about testing this but I would like to hear what others think of this option or any other suggestions too.
Does it matter if the windows are open or closed? Some cars can throb something terrible if a front window is open and the back windows are closed. If you open the back windows it goes away.
Manual transmission or automatic?
They’re different.
How many miles on your Forester?
Is it something that you can really feel, or do you just hear it?
If you can feel it, it could be a warped or loose brake rotor. I had your exact symptoms when I had that problem. That’s bad, but relatively cheap in parts and probably not hard to do (depends how the rotor is attached). It probably won’t kill you before you’re no longer able to drive it if you don’t fix it. And it could just be a matter of tightening some bolts. (If you’ve EVER had the rotors off, they could have been inadequately torqued, and worked themselves loose.)
It could be a ball joint about to fail. That’s REALLY bad, and could very well kill you. It’s really easy to tell, though…if the boots on the joints are intact and pliant, they’re almost definitely good. Fixing this will be a little pricier.
If you’re just hearing it and not really feeling it, I think the alignment is more likely, or a badly balanced wheel. If the car isn’t pulling to one side or the other, it’s less likely to be alignment, but it isn’t 100 percent out of the question.
Automatic, 71000
It happens with the windows closed.
I mostly hear it, occasionally when it sounds a bit like a knocking it’s on the verge of feeling.
Hope you actually needed that bearing and front axles. 71,000 sounds about 100,000 short of needing a bearing. Did the mechanic get in the car and drive it? If not, I would begin by finding one whose first thought will be to do just that.
The bearing did show signs of wear and pitting but they did not charge for the parts and the swapped tha axles back to the orginals so no charge for those parts, but I did pay $337 for labor which was 50% of what time they say the spent. I am still wondering if I was ripped off or not, they say the cost of the bearing replacement with labor would have been more than that alone.
You probably didn’t get ripped off. It costs about $100+ for a belt replacement.
Do you transition through the sound? That is, is just the onset occur at 60mph or does it continue at all higher speeds?
With the letting off of the throttle I’m thinking some mechanical harmonic vibrating a heat shield or something, but I would have thought that it would have occurred at some lower speed as well.
I will assume that this noise is attained at cruise conditions and not via (heavier) acceleration.