It is common to mistake a four-wheel drive (4WD) axle configuration with an all-wheel drive (AWD) axle, as both configurations transfer power to the four wheels of a vehicle. Two-wheel drive (2WD) axle configurations, which can consist of either a front wheel drive (FWD) or rear wheel drive (RWD) axle setup, are more common in passenger vehicles. FWD is more common than RWD in passenger vehicles.
Front Wheel Drive Axles (FWD) FWD axles transfer power from the transaxle differential to the hubs and wheel of a vehicle. They are commonly referred to as "axle shafts" or "front drive shafts." They turn significantly slower than a rear wheel drive vehicle's drive shaft. The speed can be measured at approximately 1/3 of a rear wheel drive shaft.
FWD axles are connected directly to the drive wheels and do not have to act through the reduction of the axle ring gear and pinion gears. They typically contain three separate shafts:
Inner Stub Shaft – The short shaft splined to the side gears located in the differential and connected to the inner universal joint. Outer Stub Shaft – The short shaft connected to the outer universal joint and the front-wheel hub. Interconnecting Shaft – The center shaft that fits between two universal joints.
Rear Wheel Drive Axles (RWD) RWD axles are virtually identical to FWD axles, with the only major difference being the direction is reversed. They are commonly referred to as "rear drive shafts." Since the weight is transferred to the rear of the vehicle upon acceleration, they can boost traction and accelerate quicker than FWD axles.
RWD axle configurations are essential in 2WD trucks, as the back of trucks are typically light in weight, and an FWD configuration will not be able to move it easily.
Four-Wheel Drive Axles (4WD) An FWD axle configuration is more complex than a 2WD axle configuration, as it requires additional parts to power all four wheels on the vehicle. They can also be referred to as "4x4" or "four-by-four" setups.
Front Engine Four Wheel Drive Diagram These utilize a transfer case, a component within the drive axle responsible for dividing the power between the front and rear axles, to spin all four wheels at the same speed. 4WD axle configurations are common for vehicles designed to handle unpaved terrains.