Trac Lok Differential Rear Axle

Rear axle of the car is one of the main units of the car with a rear drive, connects the rear wheels of one axis among themselves, as well as transmits the torque from the engine through the shaft to the driving wheels and by means of a differential allows you to rotate the wheels of the car with different angular speeds.

It consists of:

What is Trac Lok differential axle?

A differential is a mechanical device that divides the input torque of an input shaft between output shafts, called poles. It is most widely used in car drive designs where the torque from the output shaft of a gearbox (or PTO shaft) is divided equally between the right and left wheel axles

Such torque transfer is possible due to the application of the so-called planetary gear. In the automotive industry, it is one of the key parts of the transmission. First of all, it serves for transmission of torque from the gearbox to the wheels of the drive axle.

How does a Trac Lok differential work?

Why does a car need it in the first place? In any turn, the path of the wheel of an axle moving along a short (inner) radius is smaller than the path of another wheel of the same axle that moves along a long (outer) radius.

As a result, the angular speed of the inner wheel should be smaller than the angular speed of the outer wheel. In the case of a non-drive axle, this condition can be easily fulfilled, as both wheels may not be bound to each other and rotate independently. However, if the axle is a drive axle, then the torque must be transferred to both wheels at the same time (if the torque is transferred to only one wheel, then the ability to drive the car according to modern concepts will be very poor).

If the wheels of the leading axle are rigidly connected and torque is transferred to a single axle of both wheels, the car could not turn normally, because the wheels, having equal angular speed, would seek to pass the same path in a turn.

The differential allows solving this problem: it transmits torque to separate axles of both wheels (semi-axles) through its planetary mechanism with any ratio of angular speeds of the semi-axles. As a result, the car can move and drive normally, both on a straight track and in a curve.

However, in view of physics of the device, the planetary mechanism has very bad property: it aspires to transfer the received torque there, much easier. For example, if both wheels of the bridge have the same grip and force required to spin each of the wheels, the differential will distribute the torque evenly between the wheels.

But as soon as there is a noticeable difference in grip between the wheels and the road (for example, one wheel fell on the ice, and the other remained on the asphalt), the differential will immediately begin to redistribute torque to the wheel, the force for spinning which is the least (that is, the one that is on the ice).

As a result, the wheel on the asphalt will stop receiving torque and stop, and the wheel on the ice will take over all the torque and will rotate with increased angular speed, and the planetary mechanism will play the role of a gearbox that increases the speed of rotation of this wheel.

Naturally, this phenomenon greatly impairs the cross-country ability and handling of the car. In fact, according to logic of things, in the considered situation it is desirable to transfer the moment on a wheel located on asphalt that the car could continue movement.

In all-wheel drive vehicles, two axles are usually equipped with a differential, and often the differential can be found also between the axles (inter-axle differential). Thus, we get a transmission scheme, in which there are three whole differentials: two axles and one between axles.

The latter is necessary for constant all-wheel drive and torque transfer to all four wheels. After all, in the turn of the steering axle wheels (usually front) have completely different angular speeds than the wheels of the rear axle.

The inter-axle differential is designed to transmit torque from the gearbox to both drive axles with a different ratio of angular speeds. This arrangement with three differentials is one of the most common schemes for permanent four-wheel drive (Full time 4WD).

What is anti spin differential rear axle?

There are different types of differential locks, but basically they are divided into two large groups: differentials, which are locked rigidly, 100% (so-called lockers), and anti-spin differentials (or LSD – Limited Slip Differencial).

Each of these options has its advantages and disadvantages. The main disadvantage of the “hard” differential locks is their amazing ability to destroy the transmission, gearbox and rubber wear.

Conventional limited slip differentials (LSD) cannot provide optimal vehicle operation due to the effect they have on the vehicle when turning. Their properties cannot be changed while driving.

Is posi traction the same as limited slip?

There is no difference between these two. The former means that drive wheels have the same speed. The latter helps one wheel spin faster that the other. Actually Chevrolet has created the “posi-traction” name for passenger cars and it means limited slip differential.