Most of us put little thought into how our vehicle is able to move over the road. We’re content that it can do so. However, if you’re interested in learning a bit more about how your car, truck, or minivan actually works, you’ll need to know the role that the transmission plays, and what the difference is between two-wheel drive and four-wheel drive. Interestingly, it’s more than just the number of wheels operated by the transmission when you drop it into drive.
Before we dive into the topic in depth, let’s lay a basic foundation. We need to define what we mean by two-wheel drive and four-wheel drive. They’re pretty self-explanatory, really. Two-wheel drive simply means that when you press the gas pedal and put the transmission in drive, two wheels provide all the motive power for the vehicle.
In a four-wheel drive system, the number of wheels with motive power is four, not two, but that depends on whether the system is engaged or not. There are also other differences here. For instance, your vehicle could be two-wheel drive, but also front-wheel or rear-wheel drive. Your vehicle could be four-wheel drive, or it could be all-wheel drive. Let’s dig into these topics a bit.
As mentioned, two-wheel drive just means that two of the wheels do all the work when you put the transmission into drive and press the gas. However, which two wheels actually do the work? If you have a front-wheel drive vehicle, the front two wheels pull the car along, and also steer the car. If you have a rear-wheel drive vehicle, then the front wheels roll and steer, while the two rear wheels push the vehicle.
In most instances, a vehicle with four-wheel drive capabilities does not operate in four-wheel drive mode all the time. It’s generally a two-wheel drive vehicle with four-wheel drive capabilities, if necessary. Engaging four-wheel drive can be done in any number of ways. Some vehicles have locking lugs that must be engaged on the outside of the two front wheels (common with many older four-wheel drive pickup trucks). Many newer vehicles have an onboard switch that allows you to change from two-wheel drive to four-wheel drive without having to get out of the vehicle.
All-wheel drive systems are similar to four-wheel drive systems in some ways, but they’re definitely not the same. For instance, most all-wheel drive systems operate all the time, meaning that the transmission sends power to all four wheels constantly. You don’t have the option of changing to two-wheel drive. In addition, most all-wheel drive differentials cannot be locked the way they can with four-wheel drive systems.
“Drivetrain” is the term that applies to all the moving parts that make your vehicle go, including the transmission, the drive shaft, the rear differential, and the front differential (if so equipped). Here’s how that works in the real world:
The engine creates motive power that it then sends to the transmission. The transmission turns that power into torque, and transmits it to the drive wheels. If you have a two-wheel drive, front-wheel drive vehicle, the transmission turns the front wheels directly.
However, if you have a two-wheel drive, rear-drive vehicle, the transmission turns a driveshaft that runs under the vehicle to the differential, which is located at the midway point of the rear axle. The differential splits the power from the driveshaft/transmission, and turns the rear wheels of the vehicle.
In a four-wheel drive or all-wheel drive setup, there’s an additional driveshaft and differential located in the front. The transmission powers both driveshafts and differentials to turn all four wheels.
Really, there’s no contest between two-wheel drive and four-wheel drive. Both have their pros and cons. Also, a lot of it depends on where you live, the weather you must contend with, the surfaces on which you drive and other considerations. We’ll break these down for you in this section to help you understand a bit more.
Most of the passenger vehicles on the road today are two-wheel drive. That applies to cars, trucks and minivans. Remember that we’re not discussing front drive or rear drive applications. Two-wheel drive systems are preferable for those who don’t really need the extra power and performance delivered by a four-wheel drive system. For instance, if you primarily drive on paved roads, rarely venture out on anything that’s not at least gravel, and don’t need to worry about snow or ice, then two-wheel drive is the best option for you. This is due to a number of reasons.
First, two-wheel drive systems cost you less to operate. Because four-wheel drive systems require more power, they generally consume more fuel than two-wheel drive setups (usually due to larger displacement engines). Modern technology has helped to reduce this to some extent, though.
Second, two-wheel drive systems have fewer moving parts, which means less maintenance, and less chance of breakdowns. Four-wheel drive systems have many more moving parts, and that means more wear and tear, repair costs, and replacement costs over time.
While most of us get by with two-wheel drive vehicles just fine, four-wheel drive may be a necessity for you depending on where you live, where you drive, and other factors. For instance, if you regularly venture off road, you’ll benefit from having four-wheel drive capabilities. That applies whether you’re checking on your livestock on the back forty, or heading out do to some recreational off-roading (or mudding as it’s called).
Other reasons to consider four-wheel drive have more to do with the weather conditions where you live. For instance, if you live in an area where snow during winter is common, four-wheel drive is a very good thing to have. In fact, some areas actually close roads to vehicles without four-wheel drive during heavy snow events. If you’ll need to travel in these areas, having four-wheel drive is important. You might also want to invest in a set of good snow tires.
We’ll separate all-wheel drive from four-wheel drive because the system is different, and it’s generally found on different types of vehicles. For instance, you’re most likely to find all-wheel drive systems on passenger cars and minivans, as well as high-end import SUVs. Four-wheel drive is generally found on pickup trucks. All-wheel drive has the same pros and cons that four-wheel drive has, but because it is always on and relies on electronic sensors to operate, there’s a greater chance of mechanical or electrical failure, which increases your potential repair costs.
While a lot of focus is put on the type of drive system, you cannot underestimate the value of good set of tires. The right tires can actually make a two-wheel drive vehicle almost as competent on snow or in off-road conditions as a four-wheel drive vehicle. The right tires can also make four-wheel and all-wheel drive vehicles even more capable. Ideally, you should have a set of tires for summertime use, and another set for winter requirements (winter tires should have much more aggressive tread than summer tires). Note that “all season” tires are not usually a good choice, unless you don’t really need the benefits of winter tires.
Ultimately, two-wheel drive is generally good enough for most drivers. However, if you have specific needs, such as regularly going off road, or handling snowy driving conditions, four-wheel drive can be an excellent option.