RATTLING SOUND IN THE DRIVETRAIN

exhaust heat shield?

 

that would be highly unusual, but as they say, things happen.

 

I have heard of old school mechanics putting a small microphone mounted temporarily under the hood at different places and then listening to it as they re-create the conditions for the suspicious sound. Done carefully, that procedure may allow you to home in on the faulty part. The poor man's alternative is to ride with all windows down and long-suffering DW in the passenger seat, and then carefully listen for the rattle sound bouncing out from underneath the car.
BTW, if you are getting any kind of vibration or jiggling in the steering wheel that occurs with the sound, I would suspect then drivetrain and more specifically the constant velocity joints between the tranny and one wheel. But if absolutely smooth when the rattle occurs, then I would suspect a resonance problem where some part such as the heat shield around the catalytic converter, is gradually working itself just loose enough to resonate when the correct frequency and strength of input pulses is hitting it.

 

I have heard similar problems on some of my other cars and even my motorcycle. From I can figure, it is the tires! Are your tire treads getting worn properly? It sounds like you do your own maintenance, do you rotate your wheels properly? And with 70K miles you should be on your second set or tires possibly nearing the third set.

From experience on my motorcycle, I can hear a humming noise, especially in turns and at certain speeds it gets louder. I have yet to replace my tires on my motorcycle, but I am confident that's what it is.

 

i'm getting this at 40,000 miles on the oems. tread looks okay, i wonder if cross rotation would help? might need balancing too.

 

definitely more of a hum/drone. and it feels like there's a flat spot on one of them. a little vibration. depends on the type of asphalt as well.