Lately, it seems like my 09 Vibe (200,000 kms on odo) is doing this weird subtle "wallowing" in moderate winds while driving on the highway. It's like the back end feels "loose", as if it's not quite connected to the road, and the car wants to do these long S-curves in the lane. At first, since I was driving on a cleared semi-snowy road, I thought the rear tires were sliding on ice a little bit, but it's happened a few times since then, and it's definitely being caused by moderate winds. Thing is, though, I never had this issue before--it'd sway a little in high winds, like any other car, but the winds causing this particular problem now are always moderate (light winds, thankfully, don't seem to have any effect). Of course the problem is quite pronounced now in high winds, even more than in moderate winds. And it's always only at highway speeds--not urban road speeds.
Is there something mechanically that could be occurring that would allow the car to sway more in the rear end than it used to? It's definitely swaying in the rear, not the front.
2009 base Vibe, silver"