[Spridgets] Spridget Limited Slip

[derf]

And a welded diff is really a non-streetable diff.
I really like the Torsen in the Miata but it takes some
familiarization.  You know what you have with a welded diff or a
spool.
A Torsen doesn't really "lock" but it will do things a little
differently when cornering and getting on or off the throttle.
I am not familiar with the correct terms but it behaves differently
than a clutch type LSD.
I am also not sure if the Quaife is exactly a like a Torsen or not.
It is described as a Helical LSD which I believe to be similar if not
the same.  Torsen is a trademarked name.
One advantage of the Torsen or Quaife is longevity.   There are no
clutches to be replaced and it will probably run cooler than a clutch
type LSD.
I know a guy with a Torsen in his 93 Miata that has over 275k miles on
it and it is still working fine.

I think the Phantom Grip and other "diff preload" devices are kinda
gimmicky but somewhat functional.  They seem to do what they are
designed to do but I would probably prefer clutch LSD or Torsen/Quaife
for a race car or serious street car.