Four-wheel drive (4WD or 4x4), sometimes called part-time four-wheel drive, provides power to all four wheels with differentials between each of the front wheels and each of the rear wheels, but no differential between the front and rear differentials. Many four-wheel drive systems allow you to choose between rear-wheel drive, four-wheel drive high gear, and four-wheel drive low gear for extra torque. 4WD provides the best off-road performance and handling during slippery road conditions. Due to the lack of a differential between the front and rear axles, 50% of power is always being sent to both ends of the drive line, with no way to allow for slippage, which is necessary to account for the difference in speed between the ends when making turns on dry pavement. For this reason 4WD should not be used except in very slippery or off-road conditions, due to drive line bind that will occur in dry-pavement conditions which can cause serious damage to the drive line.
Disadvantages and Overcoming Them
Every vehicle has its own unique challenges, whether it lacks certain abilities, is more demanding of its operator, or has limits of capacity, all vehicles are imperfect. The following entries address overcoming these obstacles.
- Fuel Efficiency is often decreased by Four-wheel drive compared two-wheel drive, however, this difference is usually not that great and the effect can be mitigated by choosing a vehicle with a selectable rear-wheel/four-wheel system.