It's called an air locker, or sometimes people use the brand name 'detroit locker' to refer to them all.
There is probably someone who makes one for the older Nissan pickups that share the r200 differential.
When it is 'locked' it is truly locked, like a welded diff. I never thought about it, but it would be kinda cool to have a welded diff that you can turn off and on. welded diffs work great for drifting if you dont mind the initial understeer they create, (I say adjust the car to have some natural oversteer anyway).
A lot of people dont realize that a huge number of roadrace cars use basically a welded diff or a spool.
-Sean
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At a given day and a given circumstance, you think you have a limit. And you then go for this limit, and you touch the limit, and you think "okay, this is the limit". As soon as you touch this limit, something happens in you so that you can go a little bit further. With your mind power, your determination, your instinct and your experience as well, you can fly very high. - Ayrton Senna