More and more new cars are either rear-wheel drive or all-wheel drive, and all-wheel drive in particular is becoming more common. Which is better front-wheel drive, rear-wheel drive, or all-wheel drive is another story, and today we're going to talk about how Subaru's symmetrical all-wheel drive compares to other systems on the market. There's a reason Subaru touts its all-wheel drive system so much, and that's because it has a unique feature that its competitors don't have.
To understand how Subaru's system stands out, we must first understand the types of all-wheel drive systems installed in today's cars. If you own an SUV with all-wheel drive, chances are you're likely to have an on-demand all-wheel drive system. This means that the system does not always send power to all four wheels. Conversely, if the main drive wheel starts to slip, it will only send power to the other wheel, and while it is possible to own a Honda CR-V, with an AWD label, it doesn't send all power to all four wheels 100%.
The on-demand AWD system is also the most common, and the prominence of this system is fuel efficiency (at least in theory). Since power isn't always available to all four wheels and only when needed, there's less loss in fuel economy. So, if there is on-demand all-wheel drive, which does not permanently send power to all four wheels, permanent all-wheel drive is the opposite. Unlike part-time four-wheel drive or on-demand all-wheel drive, permanent all-wheel drive means that the engine sends power to all four wheels. That's Subaru's symmetrical all-wheel drive system, as it always supplies power to all four wheels.
4WD is also known as 4x4, this system does not send power to all four wheels permanently, and it is not an on-demand system because of the usual switch from 2WD to 4WD. This is the most common configuration in off-road vehicles as well as SUVs and pickups, but 4WD or 4x4 is a different story.
Subaru has a true permanent all-wheel drive system, which is what sets Subaru apart from other competitors, however not all symmetrical all-wheel drive systems are the same, depending on the vehicle installed. Why develop a different symmetrical all-wheel drive system? Subaru produces not only crossovers and SUVs, but also sports sedans as well as station wagons.
In the case of Subaru's mainstream model, the so-called Active Torque Vectoring (ATS) all-wheel drive is used. With the exception of the Subaru WRX, all CVT-equipped models are equipped with an ATS version. By default, the ATS system sends 60% of the power to the front and 40% to the rear. However, depending on the situation, the system can change its forward or backward torque distribution depending on the situation.
ATS actively and variably sends power based on the situation, rather than simply waiting for the system to detect slippage. The ATS also does not use any lock-up differentials, **differentials, or limited-slip differentials. Instead, it has a standard open differential, and the system uses a multi-plate** clutch to change the power distribution between the front and rear wheels.
ATS is for models equipped with CVT, but what about those with manual transmissions? That's where the most basic sticky center differential all-wheel drive (VCD) comes in. The VCD defaults to front and rear 50 50 separation, and the viscous coupler will deliver the power of the loss of traction to the wheels, instead of using sensors to control the loss of traction at the wheels, actively changing the power distribution.
While ATS is a common system found in Subaru's mainstream models, there is another system that is unique to CVT-equipped WRX sedans and station wagons. This is known as Variable Torque Vectoring (VTD) AWD, which defaults to 45 55 front and rear power distribution. This allows the system to be offset backwards, reducing understeer.
The system then changes the power through a planetary** differential, an electro-hydraulic transmission clutch, and a viscous-coupled rear differential. The CVT-equipped WRX is also equipped with Vehicle Dynamics Control (VDC), which allows the system to send all power to only a single wheel when needed. There is one system that has not been used on any model since it was discontinued in 2021, and that is the WRX STI, the most powerful version of the WRX sports sedan. The WRX STI features a Multi-Mode Driver Control Center Differential (DCCD) all-wheel drive system in which power is rear-offset in a 41-59 front-to-rear distribution.
The DCCD system is a state-of-the-art symmetrical AWD system with a mechanical limited-slip differential (LSD) and an electronic differential that can be automatically locked when needed or on the fly. As for these LSDs, the rear axle is equipped with Torsen LSD, while the front axle is equipped with a spiral LSD. The DCCD is also equipped with Active Torque Vectoring, which applies a tiny individual braking force to the inner wheels to help the car spin better when cornering.
Subaru has a reputation for its permanent all-wheel drive system, which is why the brand has such a strong and loyal following. There's no denying that crossovers and SUVs are popular these days, which is why among the many identical vehicles, Subaru stands out only for its permanent all-wheel drive system, when in fact all competitors use on-demand systems.
The 4WD or 4X4 is only seen in traditional non-load-bearing SUVs, such as the Toyota 4Runner and Jeep Wrangler, but in the crossover segment, Subaru's symmetrical all-wheel drive is an advantage that competitors don't have. There is another car brand that has built a strong market around its all-wheel drive system, and that is Audi's Quattro AWD system.
Most of the time, the Quattro AWD is a permanent AWD system, but the system used in the A3 and smaller models is the Haldex On-Demand System. Still, Audi's drivetrain choices are very similar to how Subaru treats its vehicles, so the two brands have built a solid reputation for their all-wheel drive systems.