Need new rear axle, how can i tell if it is locking or non locking rear diff ?

[ShadeTreeDSM]

ive had one axle in it before but forgot if it was locking or not. its a 1990 GSX, 3 bolt rear end. how can i tell if it is locking or non locking ? im getting a used axle and they need to know which one it is.

quick help will be appreciated.

thanks

[Cesar]

turn one axle and check to see if the opposite side spins in the same direction

[1992awdlaser]

It will say lsd on the rear diff cover.

[steve]

We don't have any locking diffs unless they are broken.
Your trying to find out if your rear diff have a viscous coupler. Viscous coupling unit - Wikipedia, the free encyclopedia

The factory test is to jack the rear end up, disconnect the drive shaft, and turn one wheel. If the other wheel turn in the same direction you have a functioning rear LSD, If it turn the other direction you either don't have it or it's blown.