Does anyone know anything about the R 200 LSD from Nismo... Is it any good? What is it comparable to? Here's a link...
http://www.courtesyparts.com/Merchan...de=38420-RS661

What is the difference between a clutch type differential and a mechanical type differential?

 

I haven't heard anything about that particular diff, but it's a clutch type. "Mechanical" type diffs generally refer to TORSEN diffs and helical gear diffs. (which are the same thing)

 

So an R 200 diff would be comparable to a diff from Quaife... a helical diff?

 

R200 is just the code for the rear end. Quaife is helical, yes. So is the S15 HLSD. The diff you posted is clutch type, like a I said before. THe diff you posted is probably comparable to Kaaz, and all of the other clutch type brands. I don't know how they compare though. My guess is that Kaaz, Tomei, are better than that particular NISMO model.