Vehicles come with various specifications often for purposes of marketing. In technical terms, these specifications are simply configurations of how a vehicle driving system is designed to run. For instance, vehicles might be referred to as four-wheel or two wheels to explain how the engine connects to the wheels to produce traction. The technical differences depend on the purpose of each type of vehicle which includes where it is to be driven. To understand the differences between this driving mechanisms one needs to study the mechanical aspect of their design.
A two wheel driving system is where the drive train only powers two of the wheels present in a car. A standard car has four wheels but with only two used as the drive, wheels is a perfect example of a two wheel driving system. This configuration is implemented in two ways, front or rear wheel drive. The front wheel drive has the two-wheel at the front of the car connected to the drive train with a constant velocity shaft from the engine using the transaxle (Riley et. al, 53). This system has its set of advantages compared to the rear drive wheel which includes more room for passengers and cargo, increased traction during wet weather as well as fuel economy. This is because the engine is located at the front, exerting more weight to the drive wheels hence producing an effective power response. The rear drive configuration incorporates a long transmission connected by U-joints to a differential which powers the wheels (Mashadi et. al, 36). This distribution allows for better handling and ease of servicing.
A four wheel drive, on the other hand, utilizes both the front and rear wheel drive configurations all in one vehicle to provide power to the wheels. The rear wheel drive implemented takes the same format as in the two wheels rear drive configuration. The main difference in the design is that the front wheels tap their power from the transmission and not directly as in the two wheel front configuration. A transfer case is attached to the transmission which is then joined to a drive shaft by a U-joint. The shaft then connects through differential gears on the front drive shaft connecting the two wheels as in the rear drive configuration (Miller, 36).
When a four-wheel car is moving both the front and rear wheel can be adjusted to propel it. It is important to note that even though they are always connected to the same transmission line, the two wheels rotate at different speeds only except when the car is moving in a perfectly straight line. Therefore, a differential has to be included to allow both wheels to power the car on a dry hard surface. Otherwise, the difference in terrain would tend to cause slippage hence increased tear and wear and probably a mechanical failure (Mashadi, 42). The four-wheel drive configuration, unlike the two wheel driving system, has a transfer case located after the transmission to direct power to both axles when needed.
A four-wheel drive provides more traction on most of the surfaces hence can be used in almost all weather conditions compared to a two-wheel drive. In harsh weather conditions, front wheel two drive systems provide better control of the vehicle due to increased traction compared to the two-wheel rear drive system (Miller, 39). They are therefore mostly preferred when for instance choosing family cars as they are cost effective. Two wheels rear drive prove to be the best when it comes to performance compared to the front wheel drive. When comparing the two wheel drive system to the four wheel drive system, all these advantages are incorporated in the four wheel system. It, therefore, means that a four wheel drive will provide better performance in most conditions. However, the challenge comes from the cost of maintenance. First of all acquiring a four wheel drive is expensive due to the added systems compared to a two-wheel drive. The fact that the system consists of two differential systems that power both wheels makes the cost of maintenance high. One will have to be buying oil to refill two instead of one differential compartment. In most cases, this types of vehicles experience more mechanical breakdowns due to the unbalanced and uneven forces generated from the rear and wheel (Dick, 66). Thus after a period, the car will need maintenance compared to a two-wheel drive. This makes their maintenance costly as well. The weight due to extra mechanical parts are a liability and increase fuel consumption.
Modern four wheel drive vehicles have advanced control systems that allow one to choose between low power and high power depending on the nature of the terrain. This adjustment allows for customization of four wheels for applications such as military use or industrial use. Furthermore, the control system allows the driver to switch between a two wheel driving systems for fuel efficiency and only turn on four wheel drive systems in harsh driving conditions.
Work Cited
Advanced Hybrid Vehicle Powertrains, 2011. Warrendale, PA: SAE International, 2011. Print.
Developments for Drivelines in Four-Wheel Drive Systems. Warrendale, PA: Society of Automotive Engineers, 1995. Print.
Dick, Wesley M. All-wheel and Four-Wheel-Drive Vehicle Systems. Warrendale, PA: Society of Automotive Engineers, 1995. Print.
Mashadi, Behrooz, and David Crolla. Vehicle Powertrain Systems. Chichester, West Sussex: Wiley, 2012. Internet resource.
Miller, John M. Propulsion Systems for Hybrid Vehicles. Stevenage: Institution of Engineering and Technology, 2010. Internet resource.
Riley, B S, and B J. Robinson. Handling Tests on Four Wheel Drive Multi-Purpose Vehicles. Crowthorne, Berkshire: Transport and Road Research Laboratory, 1991. Print.
Transmission and Driveline, 2009. Warrendale, Pa: SAE International, 2009. Print.
