my tires are not in the greatest condition, but on dry road the car handles perfectly and drives straight as an arrow.. but the second I hit some wet road, or less than 1mm of snow the rear end just seems like it's steering around by it's self.. There is no way it's sliding, it happens slowing down, speeding up, holding the same speed.. almost seems dangerous to drive on anything other than perfectly dry roads.
thing is that it's never always been like this.. it started to happen after I pulled out of a parking spot one day and heard a big POP or SNAP sound at first I thought I just ran over something but I'm starting to think I might be wrong.. I have not had a chance to get the wheels off but could a broken sway bar link possibly cause it to act this way?

 

Check your bushings and suspension components in the back, sounds like something snapped...

 

I think you answered the question yourself already... get some better tires...

 

take a good look at your suspension when u get a chance. sounds like something might have given out. check the bushings and the center link......

 

Are you running matched tires? Preferably 4 matching tires with similar wear on each corner, but at the very least, tires of matching size/tread/wear in pairs front and back.

Check your DTSS bushings, and the attachment bolt. The DTSS bushings (lower inside front of the rear floating hub assembly) do wear out over time - and if the bushings are shot, or the attachment bolt, or any of the three floating hub attachment bolts are backed out at all, the rear suspension geometry will change under varying loads. Mind, that should be apparent even in the dry, but the wet will definitely accentuate bad alignment and geometry; if the wheels aren't all on the same page, so to speak, they will be fighting each other to control the direction of the car, and whichever one has the most grip at a particular moment will be the one that most controls the direction of the car.

 

centerlink = sublink..........also check the 2 lateral links.....

 

I just checked and the passenger side tire is much more worn than the other, they were both put on at the same time and brand new.. yep something is messed on the passenger side. drivers side is in pretty good shape, passenger side is nearly bald.. damn!