Funny that you mention the 98-99 Sentra SE's. I have a 98 SE and it does not have a LSD in it. I have just gone through my SECOND set of spider gears in the differential and didn't feel like fixing this tranny or buying a whole new diff, although a aftermarket diff would be the best way to go in my opinion. What I did was I got a tranny from a 98 SER to replace it. It just happened that it doesn't have a LSD in it either, so you have just told me.
I guess I am stuck "one wheel squeelin' it" again. Thanks for the help.