[dogfighter]

first off i was just wondering if all the GT's came stock with a posi rear or limited slip. I have a 91 GT and it seems like sometimes both wheels burn but other times only one spins when i smoke my tires. The car has 146k miles on it and i dont know if the diff oil has ever been changed or if the diff needs a rebuild. Any help on how i can get posi 100% of the time would be great. I know i could buy a new diff like an auburn or a trak-lok diff but i was wondering if there was an easier fix. All .02s are greatly appreciated. thanks