[Vision]

here is another way similar to the first, just jack one wheel off the ground and put in neutral. spin or attempt to spin the wheel off the ground. if it spins with realitive ease it has open spiders, if it is hard to turn it would indicate a limited slip, if it turns 1 rotation or less and is unable to be turned anymore it is probally a posi.
hope this helps and it works with just about all makes.