Many people hear terms like front-wheel drive, rear wheel drive, four wheel drive and all wheel drive and only have a general understanding of what these terms mean. They all are different layouts of drivetrains but generally have the same outcome, the components that make them up transfer power and torque from the engine and transmission to the vehicle wheels. There are a lot of moving parts to this concept so first, let’s cover the basics.

Powertrain & Drivetrain

Beginning with the drivetrain, this is part of the powertrain, which also consists of the engine/motor and transmission. The powertrain is all the car parts that make the vehicle move, and the drivetrain is part of the powertrain and it connects the engine and transmission to the wheels. The two more basic types of drivetrain is 2 wheel drive (2WD), which consists of front wheel drive (FWD) and rear wheel drive (RWD).

Rear Wheel Drive (RWD)

Let’s start with what parts usually make up a RWD system:

Transmission

It connects directly to the engine and transfers the power that is sent from the engine to the wheels. It is the center of every vehicle’s drivetrain and has hundreds of moving parts that help ensure that the correct power is distributed to the wheels. Without this car part in working order, your car is completely useless, so it is worth replacing if you know how. Fortunately there are used auto part stores that can give you a quality used transmission for a fraction of the price of a brand new one. My Auto Store is a great option when it comes to buying transmissions online. Their online used auto parts will match the exact make and model of your vehicle.

Drive shaft

This shaft connects the transmission to the differential. It rotates and turns the gears in the differential to create power to send to the wheels. The shaft is connected to the transmission and differential with universal joints (U-joints). 

U-Joints

These joints are able to withstand the transfer of torque in between the transmission and the differential at various angles but cannot be pushed past certain angles or it could cause damage to the drivetrain.

Differential

This holds the gears that transfer the power from the driveshafts to the axles which brings the power directly to wheels. Can consist of different kinds of gearing that control the amount of power that each wheel receives, the different gear setups can allow both wheels to spin consistently at the same rate or it can distribute power to each wheel as needed. When a wheel slips and loses traction the gears expand and send more power to that wheel allowing the vehicle to regain control in hazardous conditions. Consists of various parts such as pinion gear, spider gear, bearings and axles.

Axles 

They are rods that connect the differential gears and the wheel, causing the drive wheels to rotate.

RWD is similar to FWD, except the engine power is sent to the back two wheels. Pickup trucks, older SUVs, sports cars, and high performance cars are usually equipped with this drive type. This helps trucks and SUVs have better traction when lugging around a heavy load. It helps high performance vehicles handle better by improving the balance of the car’s weight evenly. Now that the front two wheels don’t have to worry about steering and driving at the same time, the suspension can be optimized for more efficient handling. The downfall to this is that these cars tend to lose  traction more easily on slippery surfaces; it makes drifting very easy on the other hand!

Front Wheel Drive (FWD)

First, let’s discuss the components of a FWD car:

Transaxle

Typically found in FWD vehicles and is another name for a side mounted transmission because it combines the transmission and the front differential in one piece giving more direct power to the front wheels in a short distance. The engine is placed sideways compared to other drive types, horizontally instead of vertically like in most RWD cars.

Half shaft

One of these is on each side of the vehicle and connects the transaxle to the drive wheel and has CV joints on both sides; may also be referred to as a CV Axle.

Constant Velocity Joints (CV Joints) 

They pivot so the wheels can move because the axle is sitting at a much larger angle than a RWD drive shaft which only moves when the rear suspension bounces up and down, it is covered by CV boots. They are similar to U-joints but are able to withstand more of an angle, for more information on the differences between U-joints and CV joints check out CJ Off-Road’s explanation! 

FWD means all the engine power is sent to the front two wheels of a vehicle. Since the power goes to the front two tires a long drive shaft is not necessary, so half shafts are used instead. FWD is the cheapest type to design compared to the others and because everything is towards the front of the car. Due to this design, FWD vehicles can be made smaller and lighter, or they can be made bigger for more space. Having everything at the front of the vehicle also helps when going up hills because most of the vehicle’s weight is in the front. Although the weight of FWD vehicles are usually lighter than RWD causing these vehicles to have more fuel efficiency than others. Many part-time all wheel drive vehicles drive in FWD until they need more traction sent to the back two wheels.

Front Wheel Drive vs. Rear Wheel Drive

FWD and RWD vehicles are similar because they only send power to two wheels from the engine and transmission. They differ when it comes to what wheels receive power and if there is a rear differential or a transaxle. People who need to haul heavy items in the back of their truck or SUV and those who want better handling for performance and racing should look at RWD vehicles. People who want a daily driver that works decently in light snow/rain, is fuel efficient, and cheaper than other options, should lean towards FWD vehicles. 

If you find yourself having any troubles with your vehicle or its drivetrain check out My Auto Store, this auto parts store has the part you need. Not only do they offer the lowest prices out there but they also offer a six month warranty at any mileage and free shipping! Now that you have a general understanding of how basic drivetrains work, next up is AWD and 4WD, check out All Wheel Drive & Four Wheel Drive Explained.