4WD is a term most car manufacturers use for all-wheel drive systems . Additionally, the terms AWD and 4×4 are used. In all-wheel drive vehicles, it is possible to transmit torque from the engine to all four wheels at the same time. This improves off-road mobility and handling on slippery surfaces. The car's maneuverability is also improved, allowing the driver to negotiate sharp turns at high speed.
How 4WD works
The layout of the system may differ depending on the vehicle in which it is installed. The typical components are: a transfer case, a cardan shaft, a front and rear wheel differential and axle shafts.
The transfer case distributes the engine torque to the axles. As a rule, a reduction gear is built into the housing. This gearing is used to significantly increase the torque coming from the engine when needed.
The front and rear axles can be connected in different ways depending on the type of 4WD. Vehicles with selectable all-wheel drive are equipped with a sliding sleeve. It can be engaged with a button or lever, which activates an electric motor. From a certain position, the sleeve switches on the corresponding gears and thus firmly connects the axles to each other. This makes them spin at the same speed regardless of traction.
On vehicles with permanent four-wheel drive, the transfer case is equipped with a central differential. It can be a limited slip differential or an open differential. The latter can be blocked either electronically or mechanically. This allows the engine torque to be distributed to the wheels with better traction.
With all-wheel drive, the second axle is engaged using a viscous or friction clutch. This is activated with the help of a gerotor pump or an electric motor.
4WD on different models
| Name | Type | The operating modes | The properties | Cars equipped with this drive |
| Command-Trac | Switchable | 2WD: Only the rear axle is Engaged.4WD: Both axles are tightly coupled.Low: 4WD and a reduction gear are engaged.N: Both axles are disconnected from the transfer case. | There is no center differential.4WD can only be used off-road.You can switch between the different modes with a lever or a switch. | Jeep Cherokee XJ, KJ, SJ; Grand Cherokee ZJ; Comanche MJ; Liberty KJ; Wrangler YJ, TJ, JK, JL; Wagoneer SJ |
| M xDrive | Permanent with 2WD function | 4WD: Active power distribution between the AxlesSport: All-wheel drive with sport mode2WD: Only the rear axle is switched on. | A multi-plate friction clutch with electronic control is used as the center differential. The degree of locking determines the distribution of torque between the axles. It is adjusted via a stability control system. | BMW М5 F90 |
| Quattro generation V | Permanent 4WD | The Torsen T-3 asymmetrical locking differential distributes the engine torque in a specific ratio. When locked, the speed of both axles can be balanced. | Audi RS4 B7 8ED; S6 C6 4FH | |
| Super Select | Permanent with 2WD function | 2H: Only the rear axle is switched on.4H: The visco Clutch limits torque split between axles.4HLc: The center differential is locked.2LLc: The differential lock and reduction gear are engaged. | A transfer case with three modes of operation and one low gear. A center differential with a viscous coupling is installed inside. Mechanical locking is also possible. | Mitsubishi L200 KA, KB; Pajero Sport KH, KG; Pajero Pinin V60 |