To quote some one who summed it up better than I can from another forum,
"The Gleason Torsen diff goes back a good ways. Much like a Detroit/Dyneer/Eaton TrueTrak differential in operation. Somewhere I have the manufacturers literature from Triple D industries who made the Gleason units before the company was sold to Zexel. Ultimately, it may not be as bulletproof as a Detroit Locker in a high-shock application, but in road racing, it minimizes push and instability inherent with locker/ratchet style diffs on corner enty and exit and is much more consistent than a clutch typ posi unit in racing applications. Provides more controlled and mannerly corner entry and exit I was told by a vintage racer who used both Torsen gizmos and TrueTraks in his 65 Shelby B Production race car. Ullike a spool which is what a locker behaves like under load, it does a better job in delivering power to the tire that has the best traction. I plan to try a TrueTrak in my 68 a-sedan Mustang at Hallett this year a the Mid America Shelby Meet. The Zexel Torsen units are more expensive...."