15th Feb 2013, 10:51
It's a resonant frequency; sometimes its effect is a sound or a vibration. I remember a friend's 76 Golf; the engine would hit just the right vibration frequency to make the throttle return spring eat through its mounting like it was made of a soft metal.
22nd Sep 2013, 05:32
I own domestics, but check the differential and it could be a bad wheel bearing. It appears when you are moving only. I had that stopped, and it was the the power steering. If it's none of the above, you probably ran over a cat.