positraction is basically just GM's name for limited slip:
.. meaning the carrier will allow a limited amount of slip for normal cornering, etc but any more than that and the friction from the clutch pack will heat up the fluid and cause it to solidify, locking both wheels together. (I think the posi additive is silicone?)
theoretically and ideally you will be putting too much power to the ground for 1 tire to handle (as with an open diff) and the posi will kick in, giving you two tires with traction, helping you move forward instead of burning rubber so to speak. there is really no benefit in having posi in the snow or rain if anything its a disadvantage because driving surfaces are just plain slippery. there is no means for traction whatsoever, ie your car will slide sideways, etc... when the posi locks up in the snow or rain your entire rear end is basically floating and you cannot safely control the vehicle. On dry asphalt you should just let off the throttle and regain traction...
on the other hand, with a conventional open differential one tire should keep traction allowing you to steer, keeping you from fishtailing...
JWagner, Clark, and Gandalf pretty much said it all about open-diff drive wheels.. it is a common misconception that there is a "drive wheel".. on-road, its usually the twisting of the car and rear axle from rotating force/torque of the engine, and driveline...
anyways, malibu4door dont think your car is in any way bad because 99% of the cars on the road have the same type of differential as you..
hope this helps and if im wrong about the way the clutch-type posi works (silicone heating up and solidifying) please someone speak up, Id love to be proven wrong
Mike Reeh
Gold #34