Since the 1980s, the number of trucks, SUVs, and cars where all four wheels receive power from the engine has increased dramatically. Almost half of all U.S. passenger cars and trucks are equipped with all-wheel drive (AWD) or 4WD systems. The numbers clearly show that buyers don’t need two-wheel drive.
However, most passenger cars sold in America today use a two-wheel-drive system. The entire drive package is in front, including the engine, transmission and differential. This system is known as front-wheel drive and has been used in automobiles since the late 1970s. However, most trucks and many SUVs still use rear-wheel drive systems. This is where a long driveshaft transmits power to the wheels at the back from the engine in front.
The Jeep Cherokee’s Latitude, Limited, and Overland trims are available with either front or all-wheel drives. The Trailhawk comes standard equipped with all-wheel driving.
4WD systems typically have low and high ranges that the driver can select, often with an electronic switch.
All these options leave you wondering: What’s your best option?
It all boils down to your cargo and passenger capacity needs, as well the terrain and weather conditions you are most likely to encounter. If you live on a steep hill, there are better choices than a low-slung sports car without rear-wheel drive. A raised 4WD vehicle with large knobby tires is not the best choice for a driver whose daily commute is on well-paved streets. Let’s look at each system and discuss the pros and cons.
Front-Wheel Drive Basics
Front-wheel-drive systems can be simpler and therefore more affordable than other drivetrain systems. This has contributed to their increasing availability. However, front-wheel-drive cars are more fuel efficient.
Automakers discovered that front-wheel drive was an efficient way to get a few extra miles per gallon when the Federal Government instituted the Corporate Average fuel Efficiency (CAFE) program in the mid-70s.
It was easy to connect the engine to the front wheels using a few short-drive axles since most vehicles already had them upfront. This compact drivetrain increases fuel economy and reduces vehicle weight. It also eliminates energy losses from transferring power from the front to the rear using a separate differential and long, heavy driveshaft.
The motor’s weight should be directly above the wheels to improve acceleration and traction on slippery roads like gravel, snow, water, ice, or sand. Rear-wheel-drive vehicles often experience a problem with losing traction or “fishtailing” when they enter curves too quickly. This is why using the front wheels to pull your car around corners is important.
The Downside to Front-Wheel Drive
Front-wheel drive has its limitations. Some vehicles exhibit torque steer when the vehicle pulls to one side under acceleration. A front-wheel-drive vehicle can have a greater turning radius than a vehicle with rear-wheel drive. Because all the drivetrain and powertrain equipment are under the hood, it doesn’t allow front wheels to turn as sharply in a rear-wheel-driven application.
The front-wheel-drive systems tend to wear faster than the simpler rear-wheel-drive systems. Because of their weight, front tires can have a shorter lifespan. They must also handle the acceleration and steering forces along with braking.
Rear-Wheel Drive Basics
Rear-wheel-drive vehicles can reverse almost everything that is happening with front-wheel-drive vehicles. Standing-start performance is generally higher: When you push the accelerator pedal on a rear-wheel drive vehicle, the weight shifts to the rear end. This allows for maximum acceleration on dry surfaces. The front wheels can direct the vehicle and eliminate torque steer. A rear-wheel-drive car can be “aimed by using the gas pedal. This involves applying power to the rear end and sliding it through a corner. However, this tactic is best used by experienced drivers at racetracks.
Rear-Wheel Drive’s Downsides
Rear-wheel drive is only sometimes the best option for performance. Rear-wheel-drive cars need a driveshaft. They have a space-robbing interior hump in the middle of their passenger cabin to accommodate it. A rear differential is also required to complete the 90-degree turn that transfers engine power from the driveshaft into the rear wheels. These components make rear-wheel-drive cars more fuel-efficient than front-wheel-drive ones.
Inclement weather can make rear-wheel driving more difficult. Even though traction control is standard on most cars and trucks, rear-wheel-drive models still have a disadvantage in slippery conditions.
Rear-Wheel Drive vs. Front Wheel Drive
A front-wheel-drive system is lighter, more efficient, and lowers production costs. It also has a higher fuel economy than a rear-wheel-drive system. Because the engine and transmission are directly above the wheels, it improves traction.
Because weight is transferred to rear wheels when accelerating, rear-wheel drives offer better acceleration than front-wheel drives. This increases traction. Expert drivers can use rear wheel drive to maneuver the rear end around corners. This is an advantage in racing. Rear-wheel-drive cars have a weight distribution closer to the ideal 50 percent front and 50 percent back. This improves vehicle balance and handling.
Two-wheel-drive trucks require rear-wheel drive because the truck’s back is so light it would be difficult to drive an empty pickup if the whole drive system was upfront. Even on moderately bumpy roads, the rear wheels could be almost floating and lose contact with the road. To improve traction, you can add a load to the rear of a rear-wheel drive truck or SUV to haul cargo or tow a trailer. The driving wheels should be close to the trailer’s connection point to improve towing.
Two-wheel-drive systems have greatly improved their handling capabilities thanks to the development of antilock brake and traction control systems. For many drivers, a two wheel drive vehicle with Traction Control is all they will ever need.
The Four-Wheel World
AWD and 4WD systems provide more traction and handling capability for those who need them. Because they direct power to the wheels with the best traction, they are especially useful on slippery or loose surfaces. They are also capable of helping with towing chores, such as pulling boats up slippery launch ramps.
AWD and 4WD add more complexity to the drive system, increasing cost and weight. Although an increase in weight can decrease fuel economy, this can be offset by today’s more efficient engines (electronic, hybrid, and diesel). AWD and 4WD can increase a vehicle’s cost by approximately $1,500 to almost $4,000.
People often purchase AWD and 4WD vehicles for occasional off-road or ski trips. However, 90 percent of their time will be spent in traffic or driving on paved roads. For their daily driving, these drivers might be better off renting an AWD vehicle or 4WD truck for their ski trips. This would help them save money on their car and fuel and maintenance expenses.
AWD and 4WD have higher maintenance costs and lower fuel consumption than two-wheel-drive models. This increases total ownership costs. A lot of people find systems that drive all four wheels more practical, despite the higher price. These systems offer significantly improved traction on all surfaces and can increase towing capability depending on their type.
The additional cost of fixing damage to a two-wheel-drive vehicle with poor equipment can be negligible compared to the added burden of having to repair it. These extra costs can be offset by the fact that cars with AWD and 4WD systems usually have a higher trade-in or resale values than their two-wheel drive counterparts. This is particularly true in areas with inclement weather and difficult terrain, where such systems are popular.
You’re now convinced that you need power for all four wheels. Which system should you choose? It used to be easy to choose between AWD or 4WD. One was for cars that could drive on pavement, and the other was for trucks and SUVs traveling on rough mountain trails. These distinctions are now blurred. While many car buyers and automakers still stick to traditional labels, manufacturers tend to refrain from using these terms to fit their model lineups or marketing strategies.
However, vehicles for off-road or heavy-duty use still have to bear the 4WD label. AWD systems are available on all vehicles, including sports cars, trucks, and SUVs. They can also be found in mild SUVs, crossovers designed for soccer moms and dads, and top-of-the-line luxury models. For those who enjoy the outdoors, AWD can also be found on high-clearance models with knobby tires.
There are two types of AWD systems. Part-time AWD systems can be either automatic or part-time. This means that the vehicle operates in front-wheel drive mode, and power is delivered only to the four wheels when needed. Full-time AWD delivers power to all four wheels at all times, similar to a 4WD system. However, there is a relatively low range for serious offroading. AWD systems can also provide torque vectoring. This is where sensors direct engine power to the wheels with the greatest traction, regardless of location. AWD systems are typically used for cars and crossovers. They are most effective on asphalt, well-maintained dirt, and gravel roads.
Part-time and full-time versions of 4WD systems are also available. They are often found in trucks or SUVs that can be used on and off-road. Part-time systems work in two-wheel drive mode until the driver (or an onboard computer that monitors the traction) decides it’s time to have all four wheels do the driving. Full-time 4WD means that all four wheels are driven at all times.
4WD: The High and Low
Many 4WD systems offer low and high ranges that drivers can select, often with an electronic switch. Some systems, such as the Jeep Wrangler, have a floor-mounted mechanical lever.
The 4WD’s low setting, whether mechanically or electronically activated, provides greater torque for pulling and climbing in off-road environments. Low gearing makes it easy to descend steep slopes on uneven surfaces without overloading the brakes. For slippery conditions, such as loose sand, gravel, or packed snow, the default 4WD high setting can be useful.
A Word About Tires
A vehicle’s tires are often more important than its number of wheels. Many AWD cars are sporty and have excellent dry-road traction, but they come with summer tires that make them difficult to handle in snow and ice. A front-wheel-drive vehicle equipped with winter tires will perform better under snowy conditions than an AWD vehicle with summer tires or all-season tires.
Michelin tested this scenario several years ago. In almost all tests, the study showed that AWD cars with all-season tires performed better than front-wheel drive ones. Although the AWD vehicle was faster in acceleration, the AWD vehicle’s braking distance was much longer than that of the front-wheel-drive vehicle. Although the AWD vehicle would have won if it had all of its winter tires, this test shows how important it is to choose the right tires.
It’s all in the end.
AWD and 4WD add cost and complexity to vehicles and reduce fuel efficiency due to increased drag and weight. AWD and 4WD are becoming more common in front-wheel-drive and rear-wheel-drive cars. This has reduced the benefits for the average driver. These vehicles are still popular because they offer extra safety and security.
There is no one “best” layout for a drivetrain. Whatever layout you choose doesn’t matter as long as it works for your needs. Remember to consider how your tires will perform in the system you select.
A great car dealer will help you sort out the pros and cons of each system by working with your needs to find the best one. It is important to be familiar with the differences before you go into a dealership. This will allow you to choose the right drive system and save you from making mistakes. For example, you might want to buy something other than a 4WD heavy-duty vehicle for your commute to downtown Los Angeles. Or a rear-wheel-drive sportscar for touring Vermont’s hilly ski slopes.