Thank you all for your information. I don't have a sticker in my glove box so when I take it to my mechanic, we will look for a tag on the diff/axle someplace. But I'll take dirty's suggestion in to just add the friction modifier just to be on the safe side.
If I went with the mobil 1 75w 140, does it include the friction modifier? The reason I ask is because I didn't see it labeled anywhere, however, it does have LS in the top right corner leading me to believe it is for "limited slip".
If I do need extra friction modifiers, how much do I have to put in the diff?