Heres more info:http://auto.howstuffworks.com/differential8.htm
Follow links on the pages
Do searches for:
Zexel Torsen
Quaife
T-2,T-3,T-4 torque sensing differentials
tourque bias differentials
Black Gold
Gold trac
automatic traction management
There are many sites that have diagrams on how they work and split away views to see the internals.
Cars that use them:
Hummer, New Jeep Rubicon, Camaro, RX7, BMW,Ford motorsports sells them, Audi, Supra, most early AWD used them as well, like Subaru.
Most classic Mustangers are either classic owners or drag racers. So you won't find very many here using them. Go to any off road or 4WD site and you will find many people love to use them in the front axles of heavy duty rock crawling rigs. The trutrac doesn't cause any steering loss because of the way it works. It actualy helps steering in front axles.