What Is Differential?- Types And How Does it Work

What is a Differential?

A differential is a gear train with three shafts that has the property that the rotational speed of one shaft is the average of the speeds of the others or a fixed multiple of that average.

As part of the front and/or rear axle assembly, the differential plays an important role in your car’s turns. The differential is designed so that it drives two wheels and can rotate at different speeds at the same time. This function provides proportional speeds between the left and right wheels.

If the inner tire rotates 15 rpm less than straight on a curve, the outer tire rotates 15 rpm more than straight ahead. For example, when your vehicle turns a corner, the outside wheel has to go faster than the inside wheel. The differential distributes the same torque to both wheels.

This allows the wheels to respond to resistance or provide traction to give the wheel more resistance to turn less. The wheel with less resistance will turn faster.

Some vehicles, such as go-karts are not equipped with a differential. In this case, both drive wheels are forced to rotate at the same speed, usually on a common axle driven by a simple chain-drive device. Front-wheel drive vehicles are designed differently in that the axle and differential assembly is located in the transmission axle assembly or the transmission.

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What is Differential Gear box?

Differential gear, in automotive mechanics, gear arrangement that permits power from the engine to be transmitted to a pair of driving wheels, dividing the force equally between them but permitting them to follow paths of different lengths, as when turning a corner or traversing an uneven road.

What is Car Differential?

The differential is a system of gears that allows different drive wheels (the wheels to which power is delivered from the engine) on the same axle to rotate at different speeds, such as when the car is turning. Note that a car with four-wheel drive can have two or more differentials.

A differential is also the component through which a rotating driveshaft can change direction; for example, in a rear-wheel-drive car whose driveshaft runs the length of the car, it joins and transfers its power to an axle that runs perpendicular to the car to drive the left and right wheels.

Car Differential

How does differential work in a car?

In simple terms, a differential is a system that transfers the torque from an engine to the wheels. The differential takes the power from the engine and divides it so that the wheels can spin at different speeds. Rotate it around a corner and you won’t have any problems as each wheel can turn independently from the other.

When you look at a complete modern differential, it looks incredibly complicated.

However, if you systematically break it down and understand the basics of what it is trying to achieve and how it is trying to achieve it, you will find that it is really a beautiful thing.

Check out this video of Chevrolet engines for a retro look at the differential.

Now that we understand the basics of a differential, or in this case an “open differential,” let’s discuss a little more about a limited-slip differential (LSD).

Imagine you are on the track trying to get out of a tight corner at 50km/h. All of this power will take the path of least resistance.

All weight has been shifted to one side. All of that power will only spin the inner wheel, resulting in a tremendous amount of power lost or spinning and a major crash.

The LSD is in place to minimize this drive loss. A clutch system creates friction on each side of the axle so that the car can redistribute torque to each wheel so you can get as much power as needed. If you know your way around the wheel, you can steer the car with nothing but power, even in a curve.

As you can imagine, the entire differential mechanism has to withstand an enormous force. This is just one reason why these components are made from the strongest possible materials. No straws and milk bottle caps.

Differentials have to be extremely durable. When cars were slower and less demanding, you could get away with cheaper metals. This is simply no longer the case.

Even today’s simplest vehicles can travel comfortably at over 150 km/h and are capable of safely cornering at relatively high speeds. High-quality components are no longer reserved for the racetrack.

Parts of Differential

Following are Differential Parts:

  • Bearing kits
  • Individual seals and bearings
  • Ring and pinion sets
  • Axle shafts
  • carrier/pinion shims, pinion nuts, crush sleeves and ring gear bolts
  • posi-traction and internal gear kits
  • housings carriers
  • These are just some of the component parts in stock. We even have used parts for most differential applications.
  • Pinion Drive Gear: this part transfers the power to the ring gear from the drive shaft.
  • Differential case assembly: this part holds the Ring gear along with other components which drive the rear drive axle.
  • Ring Gear: this section transfers the power to the previous part that is Differential case assembly.
  • Rear drive axles: these are the steel shafts which transfer the torque from differential case assembly to drive wheels.
  • Axle housing: these are the metal body that encloses the rear axles and also supports the rear axle assembly.
  • Rear axle bearings: these are the ball bearings which fit between the axle housing and the axles.
  • Side gears: these gears help both the wheels to turn independently while turning.

Types of Differentials in Cars and Trucks

There are mainly four different types of Differential:

  • Open Differential.
  • Limited-Slip Differential.
  • Locking Differential.
  • Torque-Vectoring Differential.

1. Open Differential

This type of differential is often found in family sedans and economy cars. It splits the engine torque into two energy outputs to allow the wheels to rotate at different speeds. If one tire loses traction, the other will lose power to maintain traction.

A differential in its most basic form comprises two halves of an axle with a gear on each end, connected together by a third gear making up three sides of a square. This is usually supplemented by a fourth gear for added strength, completing the square.

This basic unit is then further augmented by a ring gear being added to the differential case that holds the basic core gears and this ring gear allows the wheels to be powered by connecting to the drive shaft via a pinion.

This gearing arrangement makes up the open type differential and is the most common type of automotive differential from which more complicated systems are derived.

The benefit of this type is mostly limited to the basic function of any differential as previously described, focusing primarily on enabling the axle to corner more effectively by allowing the wheel on the outside of the turn to move at a faster speed than the inside wheel as it covers more ground. It does also benefit from its basic design being relatively cheap to produce.

The disadvantage of this type is that because the torque is split evenly between both wheels, the amount of power able to be transmitted through the wheels is limited by the wheel with the lowest amount of grip.

Once the traction limit of both wheels combined is reached, the wheel with the lowest amount of traction will begin to spin reducing that limit even further as there is even less resistance from the already spinning wheel.

2. Limited-Slip Differential

Offering the best of both worlds, the limited-slip differential operates as an open differential until slippage occurs, then the differential will automatically lock. This type is found in vehicles like the Nissan 370Z and Mazda MX-5 Miata.

A limited-slip differential (LSD) is a type of differential that allows its two output shafts to rotate at different speeds but limits the maximum difference between the two shafts.

In an automobile, such limited-slip differentials are sometimes used in place of a standard differential, where they convey certain dynamic advantages, at the expense of greater complexity.

Mechanical limited-slip differentials are arguably the most common type of differential due to their wide range of applications. They work by shifting a portion of the torque to the wheel with the most traction while limiting the slip on the wheel with the least traction. Because of this, limited-slip differentials are often referred to as “torque sensing”.

Like an open differential, the wheels can rotate at different speeds. However, with a limited-slip differential, torque is not always balanced between the wheels. This allows the wheel with traction to receive more torque in order to continue to move the vehicle. In other words, the differential is said to “bias” more torque to the higher traction tire.

The amount of torque variation the differential can shift between wheels is referred to as the bias of the differential.

Disadvantages:

  • The key disadvantage, when compared to a locking differential, is that the amount of torque that can be transmitted to the wheel with traction is limited (thus the name, limited-slip). Since they cannot provide 100% lockup, during extreme situations (i.e., complete loss of traction at one wheel), there may not be enough torque to the wheel with traction to move the vehicle.

3. Locking Differential

Sometimes also known as a welded differential, this differential connects the wheels so they spin at the same speed. This typically makes turning a little more difficult. Vehicles that use this type are full-size trucks and Jeep Wranglers.

The locked or locking differential is a variant found on some vehicles, primarily those that go off-road. It is essentially an open differential with the ability to be locked in place to create a fixed axle instead of an independent one. This can happen manually or electronically depending on the technology in the vehicle.

The benefit of a locked differential is it is able to gain a considerably greater amount of traction than an open differential. Because the torque is not equally split 50/50 it can channel more torque to the wheel that has the better traction – and is not limited by the lower traction of the other wheel at any given moment.

Because you are unlikely to be traveling at speed and are usually traveling over uneven ground, the issue of tire drags and wear around corners on a fixed axle is less of a problem.

One disadvantage of locked diffs is called binding, which occurs when excess rotational energy (torque) is built up within the drive train and needs releasing – typically achieved by the wheels leaving the ground to reset the position. Or by simply releasing the locks once they are no longer needed.

Imagine a long cardboard tube held at each end, and then twisting the tube in opposite directions to the point the tube couldn’t withstand the force anymore and folds and tears that’s binding.

It happens because the wheels are moving at different speeds which twists the axles and puts increased pressure on the gears – but the load on the wheels and their increased traction is enough to prevent the tires from slipping to release the pressure.

4. Torque-Vectoring Differential

Used by the BMW X5 M or Lexus RC F, the torque-vectoring differential uses additional gear trains to send a specific amount of torque to each wheel for added control on turns.

The TVD takes this electronically enhanced system even further by using it to manipulate the angle, or vector, of the vehicle in and out of the turns by encouraging specific wheels to receive more torque at key moments – improving cornering performance.

By activating the opposite clutch to what a purely mechanically driven LSD would normally engage, you can use the effect to assist with steering while also putting more power down, overcoming the deficiencies in the LSD system.

On entry to the corner, a multi-way LSD exerts resistance to both wheels to at least partially lock the axle and stabilize it under braking – which is then released as the wheel speed drops and the vehicle turns in, allowing the wheels to rotate at different speeds.

However, instead of releasing the resistance on both wheels, a TVD continues to activate the clutch on the outside wheel only – increasing the resistance experienced by that wheel and making the system channel more torque through it. This imbalance of power to the outside encourages the vehicle to turn into the corner sharper and reducing understeer.

By continuing to apply this resistance through the corner, as the vehicle passes the apex and begins to accelerate out it will continue to override a normal multiway-LSD – which would again interpret the faster moving outside wheel as slipping and divert torque during acceleration to the inside wheel, which it perceives as having more grip.

With the TVD exerting more resistance onto the outside wheels clutch, it tricks the system into diverting more torque through it – increasing the amount of power that can be applied and reducing the understeer experienced under acceleration out of a corner.

A Torque Vectoring Differential is capable of channelings 100% of the available torque through a single wheel when needed in the most extreme of circumstances.

The downside to the system is it is very complicated and very expensive, and typically only used for racing/track applications for its high speed cornering potential.

Every system has its owns benefits and disadvantages, and although the more complicated systems are generally superior, they have an attached cost that far exceeds the simpler systems.

As with everything automotive, how much benefit you will gain from each system comes to down to what exactly you will be doing with your vehicle and what you need your differential to be capable of.

You’re not going to have much need for a Torque Vectoring Differential when visiting the local supermarket unless you fancy yourself in the next WRC and can afford the fines – but you may want a Locking Differential if you happen to live in a rural location better accessed by an off-road vehicle.

FAQ

What is Differential?

A differential is a gear train with three shafts that has the property that the rotational speed of one shaft is the average of the speeds of the others or a fixed multiple of that average.

What is Differential Gear box?

Differential gear, in automotive mechanics, gear arrangement that permits power from the engine to be transmitted to a pair of driving wheels, dividing the force equally between them but permitting them to follow paths of different lengths, as when turning a corner or traversing an uneven road.

What is Car Differential?

The differential is a system of gears that allows different drive wheels (the wheels to which power is delivered from the engine) on the same axle to rotate at different speeds, such as when the car is turning. Note that a car with four-wheel drive can have two or more differentials.

What are the parts of Differential?

Following are Differential Parts:

1. Bearing kits
2. Individual seals and bearings
3. Ring and pinion sets
4. Axle shafts
5. carrier/pinion shims, pinion nuts, crush sleeves, and ring gear bolts
6. Positraction and internal gear kits
7. housings carriers
8. These are just some of the component parts in stock. We even have used parts for most differential applications.

What are the types of Differential?

There are main four different types of Differential:

1. Open Differential.
2. Limited-Slip Differential.
3. Locking Differential.
4. Torque-Vectoring Differential.