Quote:
Originally Posted by russv
I went out and did the 35 mph and 70 mph sound test and noted the sound described at both speeds. It seems to come from the rear of the car. I think there are 3 possible theories:
1) The tires create the harmonic which is then amplified through the body of the car.
2) The exhaust creates the harmonic
3) The rear differential creates the harmonic
I'm tending to rule out the tires as the harmonics are at differing speeds. (My opinion, I could be wrong).
Having owned rear wheel drive cars in the past I have experienced drive train noise. Consider that you are dealing with 3 components: transmission, drive shaft, and differential.
I've also experienced cars with exhaust systems that demonstrate a harmonic sound, but it is usually over a certain RPM range and not necessarily speed related (Mini Cooper, various Hondas).
My money is on the drive train, probably drive shaft/differential. That said I am not too concerned at this point, unless it gets worse. Probably a normal sound.
AND, let's keep the discussion civil because it appears to be endemic to all our cars and is a concern to some.
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1) From past experience with tire noises, there is at least some change in the character of the noise depending on the road surface. I've noticed none on all the different pavement types I've driven on, including rough asphalt, smooth asphalt, concrete, etc.
2) The noise does not sound at all like it's coming from the exhaust to my ears. I have not tried clutching-in at 70 MPH to see if there is any change in the character of the noise, but I am extremely skeptical that there would be. Also, you are reporting the noise with an automatic transmission vehicle and I am seeing it with my manual transmission; the difference in gear ratios would mean that the engine is spinning at different speeds between our two cars. For us both to hear the noise at the same speed seems to rule out the engine (and my extension, the transmission and the exhaust) from being the culprit.
3) I don't recall if the final drive is a different ratio between the automatic and manual cars, but regardless, that is only one component of the differential. The LSD itself is the same. I, like you, tend to think the noise is coming from the differential or another component in the driveline.
It should not be too difficult to identify the source of the noise if we can get Subaru/Toyota interested in doing so; as I have stated before, I do not feel that the noise is normal and will insist upon it being addressed.
Quote:
Originally Posted by industrial
I've tried to listen for this resonance. I don't notice it at all.
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This is but one reason why I don't buy that the noise is normal.