4x4, AWD, and Transfer Case Systems in Vehicles

4x4, AWD, and Transfer Case Systems

Limited Slip Differential

A limited-slip differential incorporates a mechanism to mitigate the standard differential's effect during situations where one wheel loses traction. This system engages automatically without driver intervention, unlike manual lockers.

Track-Lok

The Track-Lok system is a regular differential without locking. If one wheel rotates, the opposite wheel will generate the same torque. Part of the torque transmission from the crown gear is passed through a clutch. The clutch sets contain multiple clutch discs with radial grooves on plates made of fiber material.

Track-Lok clutches are engaged by two concurrent forces. The first is the preset force exerted by Belleville spring washers within the clutch. The second force comes from the separation generated by the gears' lateral torsion applied through the crown gear. The differential compensates for rotation in minor differences, such as during turns, allowing the differential effect between axles. However, it prevents prolonged or sudden slippage by coupling all planetary discs.

4x4 Transfer Case

A transfer case is used for coupling the front-wheel drive system in off-road vehicles. This system also allows for gear reduction beyond the standard transmission. Torque can be transmitted to the front axle via robust chain plates or helical gears meshing directly or through intermediary gears in both axles. The standard ratio is 1:1.

Haldex

The Haldex system is coupled with the transmission. Its apportionment function is controlled by an electronic module that takes signals from the ABS sensor circuit and parameters from the electronic engine management system via the CAN bus. Torque distribution to the axles is determined not only by axle slippage but also by dynamic conditions affecting the vehicle. Using these parameters, the electronic module manages the Haldex system, processing information to anticipate axle slip and quickly adjust torque distribution to the rear axle.

XDrive

The XDrive coupling uses an oil-coated disc, similar to those used by Haldex. XDrive distributes torque between axles based on transportation needs, acting as a center differential. This electronically managed system is linked to the DSC stability control, which balances power distribution between axles.