If your diff has clutch packs you definantly have LSD.

Easiest way to check is jack up the rear end with the car in gear and see if you can easily rotate the back wheels in opposite directions. If it takes a reasonable amount of force to do so that is the resistance of the LSD.

 

Boo ya, or try my fav test

Cut the wheel, and drop the clutch, if your rear end slids out like fun and fun should, you got lsd. If your car goes lame on you and only spun the inner wheel you lose... like me

 

Acutally I have never tried it, and my open diff is cool, it just needs a LSD to be better

 

***EDITED***

Depends on the type of LSD. A Viscious wont have issues turning it different directions. EDIT***** This is not entirely correct. If you spin the DRIVESHAFT, then both wheels will turn the same direction with a VLSD. And 400hp930 is correct about the resistence thing


As far as the original question, YES, you can spin both without the LSD. Both of my cars do it off a hard launch.

 

Oh shit....I guess I won't find out, unless I rip it open..

 

Notice I say resistance. A viscious LSD will cause noticable resistance.

 

with my cars, if both back wheels spin the same way it's a sure grip if not then it gets replaced, but all my cars are pre 90's

 

made a mistake earlier....see my edited post.