It’s a common occurrence when driving off-road. You press the gas pedal only to see one of your drive wheels on each axle sitting motionless while the other spins. Is the axle broken? Hopefully not.

Nine times out of 10 if you hear us talking about traction-adding devices here, we are talking about lockers or maybe a spool. We generally give limited-slip diffs the cold shoulder, but that’s not to ...