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Torsen

Car culture term

Torsen
Photo: NocturnalA6 2.7 / Wikimedia Commons · CC BY-SA 4.0

What is Torsen?

A Torsen is a torque-sensing mechanical limited-slip differential that uses worm and helical gears instead of clutches to send power toward the wheel with the most grip.

Torsen is a contraction of "torque sensing," and it describes a family of gear-driven limited-slip differentials rather than a single design. Instead of using clutch packs to resist wheel spin, a Torsen relies on worm gears and helical side gears whose meshing angle makes them easy to drive in one direction but hard to back-drive in the other. That geometric asymmetry is what lets the unit resist one wheel spinning freely while the other has traction, without any electronic sensors, solenoids, or hydraulic clutches involved.

Because the effect comes purely from gear geometry, a Torsen differential reacts instantly and proportionally to torque input. When one wheel loses grip, the unit can redirect a majority of available torque to the wheel that still has traction, up to a bias ratio set by the specific gear design, typically in the range of 2.5:1 to 5:1. This makes it well suited to performance and all-wheel-drive applications where consistent, predictable handling matters more than the ultimate lockup of a clutch-type LSD. Audi has used Torsen center differentials in quattro all-wheel-drive systems since the 1980s, and Toyota, Lexus, and Mazda have used Torsen units in rear differentials on cars like the MX-5 Miata and various Lexus performance models.

The key difference from a clutch-type LSD is that a Torsen has no clutch plates to wear out and no fixed lockup percentage; it behaves purely as a function of torque and gear ratio, which means it does nothing extra when both wheels are simply coasting or spinning at equal speed with equal grip. Compared to an open differential, which always sends equal torque to both wheels and therefore lets the low-grip wheel spin freely while the high-grip wheel gets nothing, a Torsen actively biases torque away from the slipping wheel. One tradeoff is that if one wheel has literally zero traction, such as being lifted off the ground, a purely torque-sensing Torsen has no torque to redirect and can leave the car stuck, which is why some vehicles pair a Torsen with a brake-based torque-vectoring system for that edge case.

Related terms

LSDQuattroTorque VectoringAWD

Frequently asked questions

What does Torsen stand for?
Torsen is a contraction of "torque sensing." The name describes how the differential works: it responds to differences in torque demand between the two output shafts using gear geometry rather than clutches or electronics.
Is a Torsen differential the same as a limited-slip differential?
A Torsen is a type of limited-slip differential, but it uses helical and worm gears instead of the clutch packs found in a typical clutch-type LSD. Both limit how much one wheel can spin faster than the other, but they achieve it through different mechanisms.
What cars use a Torsen differential?
Audi has used Torsen units as the center differential in its quattro all-wheel-drive system since the 1980s. Toyota and Lexus have fitted Torsen rear differentials to several performance models, and Mazda has offered a Torsen limited-slip diff as an option on the MX-5 Miata.
Can a Torsen differential fail if one wheel is off the ground?
Yes. Because a Torsen only redirects torque that is actually present, a wheel with zero traction, such as one lifted off the ground on an obstacle, gives the differential nothing to work with, and the car can get stuck. Some vehicles address this by pairing a Torsen with brake-based torque vectoring.
How does a Torsen compare to an open differential?
An open differential always splits torque evenly, so a wheel that loses grip spins freely while the other wheel gets no power. A Torsen senses that imbalance and biases torque toward the wheel that still has traction, improving grip in low-traction situations.
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