Yes there are tons of threads already and i've read through most. Some questions were not answered.

My stock rear on my 89 GTA - it is either a normal "one wheel peeler" or a posi, as of yet i have not determined (though from all the leaves and snow on the roads, i still seem to move forward)

In the event it is a posi rear, how can i determine what kind of posi it is without opening it up to check? From the below link, it sounds like i may have to burnout a few times and compare the marks, or possibly wet one tire and attempt a burnout.

http://en.wikipedia.org/wiki/Limited_slip_differential

I have been reading the wiki on the different types and I am wondering: IN THE EVENT.. i do NOT have a posi, I am interested in getting one BUT i am unsure what type of posi will be the most idea for my daily driving.

Driving Conditions:
I drive in Pennsylvania, one of the WORST road systems in the US. I encounter potholes, cracks, bumps, road tar bumps, uneven pavement, different pavement textures between left and right side, Metal plates 1" above the ground you literally Bang your underside on, gravel (on the highway surfaces!) and pretty much everything you DON'T want to drive our RWD car over. During the fall there are always wet leaves across every roadway and plenty of snow and salt dust/rocks strewn about. My driving style is "cruise" typically in low RPM with OD on, rarely to i aggressively drive my car but there are times i like to put the pedal down or attempt to slide the back-end during a turn (in safe conditions mind you). Pedal presses are typically 20% throttle, only more if merging on a highway or trying to pull out in between the dense overcrowded traffic on our ancient road-systems.

I was thinking a 1.5 to balance my ability to spin both wheels while still maintaining enough overhead to roll the wheels independently. Any advice on the subject would greatly help!

 

Did you look at your RPO codes and look for G80? That will tell you if you have one or not assuming no one switched the rear end previously. Otherwise you can open the housing cover and look. A posi is unmistakable from an open differential (one has springs, other does not). Could also change the oil while doing that. Another way, jack up one side of the car so only one back tire is off the ground, put the car in neutral (make sure the car will not roll if doing this) and try to turn the wheel thats off the ground. Lastly, I do not think you have an option. Wikipedia covers all the types of positractions out there, which fbodies did not get. You either get a posi, or you don't. I'm not sure what brand the 3rd gens came with but the 4th gens came with either Auburns or Zexels depending on the year. That doesn't mean you can't buy a new one with a certain spring rate, however. Rarely do you notice that you have a posi until you need the traction. In everyday driving I can't tell my 94 has one until I floor it.

 

according to the tech data, if your profile information is correct then the 89 GTA only came with a 3.27 9-bolt with a LSD. I am not familiar with the 9-bolt, so i can't help you more than this.

 

You must find out what you have now. You need to know which rear end you have, 9 bolt or 10 bolt, and you need to know what gear ratio you have. If you have a 9 bolt then you don't have any choices except the Borg Warner cone type differential. You may already have one of these, but it might be worn out. If you do then it can be reconditioned by someone who has a lathe and knows how to do this. If you ahve the 10 bolt then you have other options, but you must know your gear ratio first. There are some differentials that are not available for some gear ratios.

 

i dont have the paper with the RPO codes anymore. my father is a reverse cleptomaniac and threw it away months ago.

upon inspecting my cars rear axle, i believe I have the 9 bolt borg-warner LSD. This would explain why with one wheel in the wet leaves and one on dry pavement, i was able to pull out of my parking spot a day ago (and why i went sideways by accident when i first got the car). Below is a pic of a borg warner (and what mine looks like).

SO question one is answered, ive got an LSD. Question two is answered, we're buggered for anything other than a posi rear. Guess ill keep what i got and like it!

 

There is a sticker on the bottom of the console lid that has all of the RPO codes for your car. It might also be on the back of the spare tire cover. This information will give you the gear ratio and differential code. There is also a tag on the Borg Warner rear end that lists the gear ratio and there will be a "limited slip differential oil only" tag too.