Helical limited slip differentials (LSDs) are one of the most popular modern differential upgrades for both street and performance vehicles.
Unlike traditional clutch-type LSDs, helical LSDs use a series of precision-cut gears to transfer torque between the wheels without relying on clutch plates or friction discs.
Because of their smooth operation, helical LSDs are the most popular aftermarket LSD upgrade the we do on a regular basis.
What Is a Helical LSD?
A helical LSD is a torque-biasing differential that uses internal helical gears to automatically transfer torque to the wheel with the most traction.
Under normal driving conditions, it behaves similarly to an open diff, allowing smooth cornering and predictable handling without harsh shuddering or banging commonly experienced in an aggressive plate type LSDs.
How a Helical LSD Works
When both wheels have similar traction:
- The diff operates smoothly
- Torque is shared between the wheels
When one wheel starts to slip:
- The internal gears create friction and resistance
- Torque is biased toward the wheel with more grip
- Wheel spin is reduced
Because the operation is gear-driven, helical LSDs are known for being extremely smooth and quiet during normal driving.
Advantages of a Helical LSD
Smooth Operation
One of the biggest advantages of a helical LSD is how smooth it feels on the road.
There is typically:
- No harsh locking action
- No clutch chatter
- No aggressive engagement
This makes them very popular in street-driven vehicles.
Low Maintenance
Because helical LSDs do not use clutch plates, there are fewer wearable internal components compared with clutch-type LSDs.
This means:
- No clutch plate wear
- No clutch rebuild intervals
- Reduced servicing requirements
Many helical LSDs can operate for very long periods with minimal maintenance beyond regular oil changes.
Excellent Street Performance
Helical LSDs work exceptionally well in:
- Street cars
- Performance road cars
- Circuit racing applications
They provide improved traction while still maintaining very predictable handling characteristics.
Quiet Operation
Compared with some clutch-type LSDs or mechanical lockers, helical LSDs are generally extremely quiet.
This makes them ideal for owners wanting improved traction without introducing additional drivetrain noise or aggressive differential behaviour.
Limitations of Helical LSDs
While helical LSDs offer many advantages, they are not perfect for every application.
Reduced Effectiveness With Zero Traction
A helical LSD requires some resistance at both wheels in order to bias torque effectively.
If one wheel becomes completely unloaded or has near-zero traction for example:
- One wheel lifted off the ground
- Ice or extremely slippery surfaces
- Certain off-road situations
the differential can behave similarly to an open differential.
This is one reason why clutch-type LSDs or selectable lockers are often preferred in serious off-road applications.
Less Aggressive Locking Action
Compared with clutch-type LSDs, helical units generally provide a smoother and less aggressive transfer of torque.
For many street applications this is a major advantage, however some motorsport or drifting applications may prefer the stronger locking characteristics of clutch-type LSDs.
Common Helical LSD Brands
Some of the most well-known helical LSD manufacturers include:
- Disctrac
- Quaife
- Eaton Truetrac
- Harrop Truetrac
- Wavetrac
- MFactory
Each brand uses slightly different internal designs and torque biasing characteristics.
Final Thoughts
Helical LSDs are an excellent option for drivers wanting improved traction while maintaining smooth and quiet road manners.
Their gear-driven design offers reliable operation with minimal maintenance, making them extremely popular in modern performance and street vehicles.
However, like any differential design, the best option depends on the intended use of the vehicle and the type of driving it will see.
At Gearhead Diffs, we regularly install and set up helical LSDs for a wide range of vehicles including street cars and performance builds.
