A vehicle’s differential is used to compensate for any differences in speed between the vehicle’s wheels, especially when cornering. The limited slip differential is more efficient than a conventional differential on specific terrains: roads and winter conditions.
What is a limited slip differential?
When a vehicle is travelling in a straight line, both drive wheels turn at the same speed. But when cornering, the inside wheel travels less distance than the outside wheel. If the engine transmits the same speed to the wheels, the inside wheel will slip, and on hard ground, the gearing mechanisms will be put to the test.
The differential is there to correct this defect. If the average speed of the two wheels will always be equal to that transmitted by the engine when cornering, the speed of the inner wheel will be lower than that of the outer wheel.
Interest in the limited slip differential
The fault of the differential appears when the vehicle gets stuck: it is enough for one wheel to be on soft ground for the car to slip. Indeed, the rotational force will be transferred entirely to the wheel that does not offer any resistance to the detriment of the wheel on the hard ground that will have a zero speed.
Although most passenger vehicles are equipped with conventional differentials, some cars that have to drive on roads or in winter conditions (ice, snow, mountains) are equipped with a limited slip differential, which partly eliminates the risk of getting stuck.
This system allows, from a given speed difference between the 2 wheels, to transfer the rotation force to the wheel with the best grip. It is activated at a minimum torque of 30% (production vehicles) to 80% (competition vehicles).
Variations of the limited slip differential
Limited slip differential with clutch
From a predefined value, the difference in wheel speeds compresses a multi-plate clutch which then connects the two axles.
Viscous-coupled limited slip differential
The clutch operates on a hydraulic principle found in the clutches used in automatic cars (torque converter).
When the difference in rotation becomes too great (in the case of a wheel that slips), oil between the two creates a hydrokinetic force that couples them and locks the differential.
This differential uses the principle of the worm screw and its irreversibility: the drive is only possible in the direction of the pinion screw drive, which makes the differential rotation of the shafts impossible.
A variant often proposed by manufacturers is a traction aid using an electronic wheel anti-lock. When the system detects an abnormal wheel rotation speed, it acts on the wheels’ braking to limit this effect.
These systems do not have the effectiveness of a limited slip differential.
Maintenance of the limited slip differential
Maintenance is the same as conventional differential, including oil level checks and recommended oil changes.
As the mechanisms are more stressed, a higher quality oil (specific 75W-90 synthetic oil) and more frequent oil changes are recommended (20,000 to 40,000 km).
Equip yourself with a limited slip differential
If your vehicle is not equipped, it can often be fitted with a limited slip differential.
If you have perfect mechanical knowledge, you can do the operation yourself: replacing the original differential with the limited slip one. You must remove and disassemble the axle or transaxle to perform the operation. The cost of the parts ranges from $1,000 to $1,900.
Otherwise, the additional labour cost will be around $500 to $800, for a total cost of $1,500 to $3,000.
In conclusion, a limited slip differential is a valuable enhancement for vehicles operating in challenging conditions, providing improved traction, stability, and overall performance. Consider equipping your vehicle with a limited slip differential to enhance your driving experience and confidently tackle various terrains.