Power-lock has 4 spider gears, Trac-lock only 2.
The Powr-Lok is one of the most aggressive and strongest limited slips ever designed. It uses a two-piece case and six forged internal gears for added strength. The Powr-Lok uses a ramping-clutch design to become more aggressive as tire-spin increases. The composite clutches provide long life and high performance. All units are Rebuildable