MKIII Differential
 

How can I determine whether my 89 Supra has a standard or limited-slip differential ? I want to change the differential oil and I understand that the recommended gear oil is not the same for both differential types.

The easy way. Chock the front wheels, jack up one rear tire until it is clear of the ground, Put the transmission in neutral, and release the parking brake. If the tire is hard to turn, you may have limited slip. If it spins easily, you have a standard diff. If it is hard to turn, jack up both rear tires clear of the ground, and spin only one. If they turn evenly, you definitely have limited slip.

^^^what he said, but also you can look in you owners manual and it will tell you what the code is for limited slip or not and then you can look in your door jam

Maybe yes, or no
 

You may have a LSD diff, but the clutch packs may be worn out, so it will act like a 'regular' diff.

Just put in Amsoil Gear Oil (it works in both types) and move on to other things.