Jeeps and Differentials

Differentials Explained

Ask any Wrangler enthusiast the one quality they expect most from their off-roader, and chances are the answer you will hear most is high performance and the ability to navigate rugged terrains with ease. In hopes of improving the performance of their beloved vehicle, some will first invest in better off-road tires to provide improved traction necessary for their adventure.

What many Wrangler owners are oblivious is that although having good off-road tires is crucial, transmitting the proper power to these tires is more critical.  There should be a proper system to transmit and distribute power to the tires and help them turn effectively. That’s where the differential comes into play. Having the correct differential will improve traction of the wheels, the vehicle’s handling and add more fun to your rendezvous.

This article will try to explain deeper the role of the differential, different differentials types and their effect on a vehicle’s handling and traction.

 

What is the Role of the Differential?

The differential comprises of a set of gears enclosed and located centrally at the point where the driveshaft intersects with the rear or front axle. The role of the gears is to receive and convert the driveshaft’s rotating motion and then split the resulting power to each axle shafts.

The differential performs three critical functions; slows down the speed of the driveshaft, transmits power from the vehicle engine to the wheels and allow different speed rotation of the tires. The differential system is advantageous especially when negotiating corners whereby the outer wheels travel a longer distance than the inner wheels.

Types of Differentials

There are four types of differentials;  Open or Standard Carrier Differentials, Limited Slip Differentials, Locking Differentials and spool differential. They all limit the spinning of the traction-less (except for open differential) and therefore offer different handling characteristics.

Standard Carrier or Open Differential

Most OEM vehicles come with this type of differential. It consists of an open carrier which holds the ring gear and spider gears. The spider gears enable the outside wheels of the vehicle to turn quicker than the inner wheels during turning. This property makes open differential advantageous for vehicles driving on modern roads.

The major problem with open differential vehicles is that it gets stuck easily in traction-less grounds (such as muddy areas or when it hits a ditch). The differential, in this case, will transmit more power to the tire with least resistance while transmitting no power to the other wheel on the same axle, this leads to the traction-less wheel spinning freely while the other remains stationary.

Limited Slip Differentials and Positraction

Positraction is a term introduced by General Motors to refer to their limited slip differential vehicles. Limited Slip differentials are designed to correct or reduce the limitations that arise from an open differential system. These differentials will distribute equal torque to both wheels on an axle when traveling straight. However, when one tire loses traction torque will automatically be sent to the opposite tire which has traction, hence preventing loss of torque to the slipping wheel.

The difference between these two differentials is that positraction aims at sending power to the traction wheel until same control is returned to the slipping and traction wheel, while limited slip differential allows wheel on traction to have higher power than slipping wheel. Positraction differential is ideal for muddy or wet roads while the limited slip differential is useful in hard-corner turning.

The two differentials, however, cannot provide 100% lockup of the differential in some situations such as when a wheel completely loses traction.

Lockers (Locking Differentials)

A locking differential uses a mechanism that permits both wheels on the same axle to rotate in unison (at the same rotational speed) hence making the axle act as a common shaft. Locking differential is designed mainly to overcome the limitation of a standard differential completely. This means that in a case where the vehicle gets stuck in a ditch, equal power will be sent on both tires unlike in a standard carrier differential. In the same situation, a limited slip differential will direct some power to the wheel on the ground which may not be enough to provide forward momentum.

Locker differential mechanisms can be classified into two; On-Command (selectable Lockers) and Automatic Lockers.

On-Command lockers (selectable lockers)

These lockers offer the benefits of both the open differential and locking differential. The locker is engaged either by using a switch or lever.

When engaged, the differential locks up both axle shafts, therefore, allowing the wheels to spin at same speed.

If not engaged, the system acts as an open differential with easy handling characteristics. The on-command locker can be found in Jeep Wrangler Rubicons.

Advantages and Disadvantages of On-Command Lockers

Advantages :
•    Acts as a regular open differential when disengaged.
•    Provides accurate control when engaged.
•    Doesn’t hinder road handling when disconnected
Disadvantages:
•    Can cause severe damage to the differential if you forget to disengage it.
•    Complex to install.
•    Costly.
•    Has more components, thus more prone to failure.
•    Has to be activated manually.

Automatic Lockers

Automatic locking differentials automatically lock both tires of an axle when torque is applied, thus allowing both tires to provide power.  The differential is, however, allowed to unlock when power is not being applied. The outcome of this is the difference in tire speed when negotiating turns. Locking and unlocking make handling vehicles with this mechanism difficult.

Examples of automatic lockers are;

  • Aussie Locker
  • Detroit Locker
  • Detroit EZ Locker
  • Fozzy Lockers
  • Lincoln Lockers
  • Lock-Right Lockers
  • Lunchbox Lockers
Advantages and Disadvantages of Automatic Lockers

Advantages:

•    Always available when you need it.
•    Easier and faster to install.
•    Budget Friendly.
Disadvantages:
•    On-road handling is hindered.
•    You might feel a slight resistance while negotiating sharp turns.
•    Increased likelihood of tire skip during cornering.
•    Makes an “annoying” clicking sound.
•    Handling is limited in snowy conditions.
•    Always activated until you release your foot off the accelerator.

Spool Differential

Spool Differential is simply a vehicle with no differential at all. They, therefore, offer 100 percent lock-up between tires. They are used in dedicated off-road and racing cars and there are no Jeep vehicles with this type of differential from the factory.

 What are Lockers Used For in Jeep Wranglers?

Lockers can be used in various situations such as self-recovery, recovering other stuck vehicles and also extreme off-roading such as rock crawling. Situations like rock crawling involve loads of traction change while maneuvering through different angles and rocks, meaning it is more likely for the wrong wheel to start spinning. Another probable situation you are likely to face when rock crawling is when your Wrangler lacks enough articulation thus causing one wheel to lift off the surface unintentionally. Lockers provide your Wrangler with more traction when needed, whether you are enjoying an off-road escapade of pulling a car out of a ditch.