Gray,
Look on the VIN Plate, under the bonnet, on the bulkhead just left of the fuel filter. All along the bottom is a number that says something like
24V FK10 G975 R150F
It all means something: the last group is your gearbox; the group before that is your diff and that's the one you need to look at. G is light duty 8 inch ring gear, 97 is a code for the gear ratio (look on the table in post #2 from Mud - but it isn't a comprehensive list). Now the answer to your question; if the last digit in this group is odd then you have an LSD, it will be 3 or 5. If not then your diff is open. Let us know what you have got.