Locking or not differential?

[lightning mobile lube]

Hey yall I put a hole thru my tranny housing so I need to know if I have a locking differential or not... Is there like a number in the VIN that will designate this, or do I actually have to take the thing out and look for the number stamped on the side? And, Are they interchangeable? I mean if one's better than the other for various reasons is there any reason I couldn't pick which one I want?

 

[lightning mobile lube]

Okay! I got it figured out! Took a bit of research, but here it is for all to see! You see that silver plate on your firewall (mine's towards the passenger side)? Look at the code for transaxle and it'll have a number. Myne says
RS505FV. I imagine the autos have a different code, but that 'V' at the end denotes locking differential. any other letter means its open, so for those of you who are interested in this thing for yourselves, or you need to replace your CV axles or boots..