How can i tell if my 1996 chevy camaro has possi traction or not?

Find a patch of dirt, put both back tires in it/on it, punch the throttle until the tires spin, get off the throttle, drive the car forward a few feet, get out and look to see if both tires broke loose in the dirt. If only one tire spins, either you don't have posi, or the posi unit is worn out, which can happen in some cases.