I'd say: forget about it!
By now, the viscous unit from 90-93 is dead.
Try better to look for 99+ differential from 5speed with shafts.
99+ 5 sp, have the same ratio as Your 1.6 Miata - 4.3 :1.
Torsen will cost $400- $850, open from $200.

Kempi



"Don Benton" > wrote in message
...
> Hopefully my last question on differentials.
>
> I can't seem to locate the '94+ parts, but one outfit quoted me $350
> for a locking differential out of a '93. I recall reading they
> weren't particularly effective, but my question is, are they any
> stronger than the non-lockers for those years?
>
> DonB
> '91 white