Why is it important to know how all wheel drive works on your car? First, it may appear that its all wheel drive system is not meant to be used on a road. For example, part-time all wheel drive cannot be used in non-slippery conditions – you’ll have to drive such car in rear wheel drive mode, even when it is raining or snowing – in the weather conditions where all wheel drive might be needed. Second, depending on the type of all wheel drive, your car behaves differently when driving and cornering in slippery conditions. You might want to know what to expect.
Don’t get confused by abbreviations that manufacturers use: “AWD” is not necessarily a full-time all wheel drive, “4WD” is not just for off-road vehicles. There is a dozen of brands car manufacturers are using to distinguish their four-wheel drive vehicles – “quattro”, “4motion”, and so on. However, these rarely indicate the type of all wheel drive system that is used on a particular vehicle.
This is an irreversible all wheel drive or permanently involved all wheel drive system. All wheels are powered whatsoever times. The automobiles with full time all wheel drive are equipped with a facility differential that lets each wheel traveling various ranges while transforming. This type of all wheel drive can be utilized both on and also off road. In slippery conditions, the center differential can be secured, whether by hand or instantly, depending upon the car.
When a hand-operated center differential lock (available on off-road vehicles as well as some SUVs) is involved, the transmission’s behavior resembles part-time all wheel drive, i.e. the front as well as rear driveshafts turn at the exact same rate of speed. Using full-time all wheel drive with locked facility differential is limited to surface areas with reduced grip.
In situation of automated lock, a Torsen differential, viscous coupling, multi-plate hydraulic clutch, or comparable grip control device is used combined with the center differential. When a wheel slips on one of the axles (one driveshaft rotates faster than the other) the tool locks the center differential and twist is moved from the axle that slides to the various other axle that has grip. As soon as the wheel slip is eliminated, the device unlocks.
Some vehicles (Land Rover Discovery II, pre-xDrive BMW X5) do not have a locking center differential, but are outfitted with an electronic traction control system (referred to as Electronic Differential Lock – EDL) on all four wheels. This digital system discovers slipping wheels by reviewing ABDOMINAL sensors, then it applies brakes to slipping wheels and twist gets moved to the wheels that have grip. While it performs well on slippery roads, the system could not take on a real mechanically securing differential when driving off-road.