hay guys im trying to figure out if 81 to 87 4x4 blazers have rear ends where both tires spin (i forgot what its called)and if any other years have it. thanks

 

The term you're looking for is limited slip or in the case of GM, Posi-trac. It all depends on the options installed from the factory. On my 2000 Bravada (and earlier, but how much I don't know), they listed the RPO codes which detailed all of the installed options. In my case, the G80 code is for a factory installed posi-trac rear end.

 

my 92 s10 blazer 4wd doesnt have limited slip, only my right rear tire has power, atleast only the right side gets power during a burnout

my 94 blazer also does not have limited slip, both only have the power in right rear

 

G80 is the code you should have in the glove box if you have the factory limited slip.

If not, there are several ways of dealing with it.
Install a axle with the posi-trac unit, make sure it has the same gear ratio as your current axle.
Install a locker.
I'd recommend welding the gears together, however I doubt this is an off-road toy.
Or you could do it the cheap way, lightly keep your foot on the brake when the back tires are spinning. This causes the power to go to both tires. On the street, its called power stands, or brake stands. This is how you can get both tires to leave rubber on a truck without a locker.