The factory LSD is not a Torsen style differential like the previous generations. Instead Mazda cut some costs here by running a Tochigi Fuji Sangyo unit.

This Quaife unit powers both drive wheels under all conditions, instead of just one or a combination of scenarios where one wheel is favored. With the factory open differential, power is lost when wheel spin happens. With the factory LSD, power is lost when the cone style LSD washes between your rear wheels in a method that seems unintentional and sloppy. 

As you might understand, an open differential transfers power to the wheel with the LEAST amount of grip (the path of least resistance). This Quaife unit does just the opposite. It mechanically reacts which wheel has the most grip or resistance and biases power to that wheel. It does this more consistently than a factory LSD, allowing you to roll into power earlier when exiting a corner.

For those of you running any sort of power adders or our own Fab9 EFR Turbo System, this unit is a MUST. It's a bit like training for a marathon and then competing on one leg (hence the term pegleg differential). All the power in the world doesn't mean anything unless it can be applied.

This diff operates in an ideal manner under any driving condition:

• Straight line: Near 50/50 operation
• Road Racing: The diff favors the outside wheel, reducing inner wheel spin, allowing the driver to accelerate earlier.

The strength of this unit is also superior since it's a clutch free, gear operation differential. Nothing to "slip" during bias changes or weight transfers. Other designs feature locking mechanisms that cause unwanted and potentially inconsistent operation, giving the drive one more thing to correct or compensate for while driving.