good 4 bolt rear?

[90 TSI FWD]

i went to the junkyard today and found a 4 bolt rear end on a 91 talon. this is obviously an upgrade on the car and it was stripped entirely except for it, so i'm wondering how you can tell if it's still good.

the rear seems like there's a black layer of grease coating on the back of it, but maybe you guys could give some input with my pics. when i turn the driveshaft, theres probably 1mm of play before the splines in the diff turn.

please respond soon because i want to put this in this weekend.

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[Deadly BlaZe]

You won't really know anything until you open that case up. And you better hope that who ever did that swap didn't take the differential apart and not set the gear backlash/preload.