Originally Posted by cheers007

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?

Originally Posted by cheers007

Dirty, is there a website I can put my VIN number just to see if it has Lim slip diff?

Originally Posted by dirtydog

Just back up onto grass or some loose dirt and punch the gas. You'll find out right away.
If you have ice around???, drive one rear tire on the ice and see if the truck moves. Doesn't matter which tire goes on the ice. Open diff will spin. LSD won't.
Just a thought