Differentials: LSD Types and Upgrades
The differential is the component that splits torque between the two wheels on the same axle. On a rear-wheel-drive car, it sits between the rear wheels. On a front-wheel-drive car, it is integrated into the transaxle. On an AWD car, there is a center differential (or transfer case) plus a front and rear differential. The type of differential your car has determines how power is distributed — and that has a massive impact on traction, handling, and how the car puts power down.
Open Differential: The Problem
Most non-performance cars come with an open differential. An open diff uses a simple gear set that always splits torque equally between the left and right wheels. That sounds fair, but it has a critical flaw: if one wheel has less traction than the other (hitting a wet patch, going over a bump, or the inside wheel unloading in a corner), the open diff sends all the torque to that wheel — the one with the least grip.
You have seen this in action: a car stuck in snow, one wheel spinning freely while the other sits still. That is an open diff doing exactly what it is designed to do — and it is exactly what you do not want in a performance application.
With a high-power car, an open differential means one-wheel burnouts when you want two-wheel traction. It means the inside rear wheel spinning uselessly through a corner while the outside wheel — the one actually carrying the load — gets none of the torque. It is a fundamental limit on how much of your engine's power actually reaches the road.
Limited-Slip Differential (LSD): The Solution
A limited-slip differential limits the speed difference between the left and right wheels, ensuring that both wheels receive torque even when one has less traction. When one wheel starts spinning faster than the other, the LSD engages and transfers torque to the slower wheel (the one with more grip). The result is dramatically better traction out of corners, more predictable oversteer, and the ability to actually put your power down with both rear tires.
Many performance cars come with some form of LSD from the factory, but the type and quality vary significantly.
Types of Limited-Slip Differentials
Clutch-Type LSD
Clutch-type LSDs use a stack of friction clutch plates that engage when there is a speed difference between the wheels. Spring preload and ramp angles determine how aggressively the diff locks.
- 1-way: Locks only on acceleration (power-on). Free on deceleration.
- 1.5-way: Full lock on acceleration, partial lock on deceleration.
- 2-way: Full lock on both acceleration and deceleration. Preferred for drifting because the rear stays locked through transitions.
Pros: Aggressive lockup, tunable (different ramp angles and preload settings), strong initial bite. Cons: Clutch plates wear over time and require rebuilding (typically every 30,000-60,000 miles depending on use). Can chatter or clunk at low speeds in tight parking lot turns. Requires LSD-specific differential fluid.
Popular options: OS Giken, Cusco, Kaaz, ATS. OS Giken is widely considered the gold standard for clutch-type LSDs — their Super Lock units are used in professional racing worldwide.
Helical (Torsen-Style) LSD
Helical LSDs (also called torque-sensing or worm-gear differentials) use helical gears instead of clutch plates. The gear geometry creates friction when there is a torque difference between the wheels, which biases torque to the wheel with more grip. The Torsen (short for "torque sensing") is the most well-known brand, but the technology is used by many manufacturers under different names.
Pros: Maintenance-free — no clutch plates to wear out. Smooth operation with no chatter or clunking. Uses standard differential fluid. Progressive engagement feels natural and predictable.
Cons: No preload — at rest or with one wheel completely off the ground, a helical LSD behaves like an open diff. The locking effect is proportional to input torque, so at very low torque (like creeping through a parking lot), it provides minimal locking. Not as aggressive as a clutch-type LSD — some drivers find it too subtle for track or drift use.
Popular options: Wavetrac, Quaife, Peloquin. Wavetrac is notable because it includes a preload mechanism that overcomes the traditional helical LSD weakness — it maintains some locking even with one wheel unloaded.
Electronic LSD (eLSD)
Electronic LSDs use a multi-plate clutch pack (similar to a clutch-type LSD) but control engagement electronically via a computer. The car's stability control system monitors wheel speed, steering angle, throttle position, and other inputs to determine how much locking to apply in real time.
Pros: Infinitely variable locking from 0% to 100%. The computer can react faster than any mechanical system. Can be tuned via software to behave differently in different driving modes. Factory eLSDs in cars like the BMW M3/M4 (F8X and G8X) are remarkably sophisticated.
Cons: Complex and expensive to repair. Can overheat under sustained aggressive use (track days). The electronic control can feel artificial to some drivers who prefer the mechanical feel of a clutch-type LSD. Limited aftermarket upgrade options — you typically work with what the factory gives you.
When to Upgrade Your Differential
Consider a differential upgrade when:
- Your car has an open diff and you are adding significant power — an LSD will transform traction
- Your factory LSD is worn out — clutch-type LSDs lose effectiveness over time and may need rebuilding or replacement
- You are tracking the car — a quality LSD provides more consistent corner exit traction
- You are drifting — a 2-way clutch-type LSD is essentially mandatory for controlled drifting
- You want better wet-weather traction — an LSD dramatically improves power delivery on slippery surfaces
Installation Considerations
Differential upgrades require removing the differential carrier from the housing, which means draining the fluid, pulling the axles, and accessing the internals. On some platforms, the entire differential assembly (pumpkin) can be removed as a unit, making the swap straightforward. On others, the work must be done in place, which is more labor-intensive.
Budget $500-$2,000 for the LSD unit itself, plus $500-$1,000 in labor. OS Giken Super Lock units are on the higher end ($1,500-$2,500+), while Quaife and Wavetrac helical units are typically $800-$1,200.
The Bottom Line
If your car has an open differential and you are making more than stock power, an LSD is one of the most transformative upgrades you can install. It does not add horsepower, but it ensures the horsepower you have actually reaches the pavement through both wheels. For track use, a quality LSD is as important as the engine tune. For street use, it makes the car more predictable and more fun in every situation where you apply throttle out of a turn.