And, it is addressed in the Owner's Manual. You all did read every word of it right?

 

In channel vent visors got rid of all the noise for me, or was it because i couldn't stop my ears from bleeding?

 

The first time it happen to me , I thought the passenger rear of the car broke away .
I drive with the fronts down , And the rears open an inch or two. Cures it .

 

I had this happen about 10 years ago in another car and have had it happen in many others since.

I new right away what it was when my son put down the back window.

Welcome to the world of laminar flow and aerodynamics.

Now we all know what it is like to be a ant in a pop bottle someone is blowing over the opening.

 

yep very common problem with lots of cars these days, and not just cheap cars my 2000 lexus RX300 did the same only i do believe it was worse, it did the same thing with the sunroof open all the way as well.. i find that it actually keeps your car cleaner if you smoke it it, open the rear 1/4 the way down and the front an inch and.. voila ashes and smoke and pulled right out if you hold it by the window

 

I have a 95 Blazer that is very noisy and gets a lot of buffeting with the rear windows down just like my HHR. Wind testing would be done with the windows closed.

 

85% of cars on the road drive with the windows up. Also to get the best MPG the wind tunnel is used to shape the body for less drag not for you to drive with only the rear windows down.

CAFE is more important than one rear window down to the mfg anymore.

 

I did see it addressed in the owners manual and just happened onto that part right after I bought it. My wife's 2004 Cavalier (renamed the HHR dent giver) also does it. If the back windows are down all the way you can crack the front, or in my case open the sunroof, and it will cure it. You just can't drive with the rear down all the way and nothing else opened.

 

Glad I saw this thread. I wasn't aware of this problem in cars these days. I normally have the front window open a bit if the back is open anyway as I crack the back to vent the front. I guess with this habit I haven't noticed it in my other cars if they do this. I would have freaked though with my new to me HHR if my daughter were to let down the back window and the entire car were to start howling.

 

Oh, It does not howl, it shudders and shakes to the extent you will think you are on a never ending washboard clay and gravel road!

In my own aesthetic the HHR just is not conducive to driving with any windows open; if you open the driver's window it blows into your eyes, then you open the rear window solves that prob, but then you cannot hear the radio, phone etc. Anyway I have decided that on the hiway the windows closed using climate control is the only "comfortable" option. The AC is not that expensive.
(Sorry, I needed the pickle)