Toyota All-Wheel-Drive Systems Explained: How They Work
Toyota Goes All-In on All-Wheel Drive
More on Toyota's All-Wheel-Drive!
Hooning the 2020 Toyota RAV4 TRD Off-Road and Hybrid in the Snow
Hooning the 2020 Toyota RAV4 TRD Off-Road and Hybrid in the Snow
In an automotive market that's going crazy for crossovers and SUVs, one of the easiest ways to add to a vehicle's consumer appeal is to jack it up and/or give it all-wheel drive. That's part of why Toyota all-wheel-drive systems are making a comeback on a variety of models.
Signature Toyota machines like the Prius hybrid and Camry midsize sedan faltered somewhat at dealers in 2019—year-over-year sales of the Camry were down 1.9 percent, while the Prius slipped a staggering 20.4 percent, far outpacing the industry-average decline of 1.4 percent. To stem the slide, the 2019 Prius received an all-wheel-drive option, and the 2020 Camry is following suit alongside the 2020 Avalon fullsize four-door. Unlike some automakers, Toyota is reinvesting in its cars, recognizing the potential in those products (particularly considering there are only two other four-door sedans that offer all-wheel drive: the Nissan Altima and the Subaru Legacy).
Toyota all-wheel-drive expertise goes back a long time. Back when "crossover" was a term used by DJs and not car shoppers, the Japanese automaker offered a rally-bred all-wheel-drive system called All-Trac on the Camry and Corolla sedans, Celica sports car, and Previa minivan. Unlike those early four-wheel-driven Toyota cars, the systems used in today's Camry, Avalon, Prius, RAV4, and Highlander bear no specific branding—rumor has it Toyota let the All-Trac trademark lapse, though we think it's high time it comes back, if only to channel the WRC glory of those old Castrol-branded Celicas.
'90s rally-car nostalgia aside, let's delve into some of the particulars surrounding Toyota all-wheel drive, shall we?
Dynamic Torque Control AWD
The most basic Toyota all-wheel-drive system is found on the Avalon XLE and XLE Limited; Camry LE, Camry SE, Camry XLE, and Camry XSE; and the RAV4 LE, RAV4 XLE, and RAV4 XLE Premium. Called Dynamic Torque Control AWD, the system includes a transfer case integrated within the transmission with a driveshaft that leads to the rear wheels. An electromagnetic coupler between the driveshaft and the rear differential engages and disengages as needed, altering front/rear torque split between 100:0 and 50:50.
The system isn't able to vary power sent right and left once it hits the open rear differential, however. Instead, if the traction control system detects wheelslip on one wheel, it applies the brakes on that corner alone, equalizing the traction between both wheels and helping preserve (or re-initiate) forward momentum. However, braking to provide thrust is as counterintuitive as it sounds, even if it does effectively help route power to the wheel with grip.
Another limitation to the base system? The driveshaft is always spinning, even if the coupler isn't engaged, leading to some additional parasitic drag in the driveline. As equipped in the Camry, Toyota acknowledges a 3-mpg combined drop in EPA fuel economy testing due to the all-wheel-drive system.
Dynamic Torque Vectoring AWD with Driveline Disconnect
Solving some of those woes in other Toyota all-wheel-drive offerings is Dynamic Torque Vectoring AWD with Driveline Disconnect. This surprisingly sophisticated system is found in the RAV4 TRD Off-Road, Adventure, and Limited, as well as the Highlander Limited and Highlander Platinum. As on the more basic system, the all-wheel-drive transfer case is integrated into the transmission, but between it and the driveshaft is a dog clutch that can completely disengage when only front-wheel-drive is needed, reducing drag on the system.
A second dog clutch between the driveshaft and the rear differential further improves the system's flexibility in metering out power appropriately. What's more, clutch packs in the differential itself provide active torque vectoring—when one wheel loses traction and starts spinning, the clutches engage, sending power to the other wheel. By reducing its dependence on the brake-based traction control, the system is even better at keeping the vehicle moving forward.
The Toyota Highlander L, LE, and XLE use a similar all-wheel-drive system with a driveline disconnect, except they forego the dynamic torque vectoring component in favor of a simpler open differential that uses traction control to prevent wheelspin.
Electronic On-Demand AWD
It seems as though hybrid technology has the potential to make driveshafts of any kind obsolete. Don't believe us? Take a look at the Toyota all-wheel-drive setup found under all trims of the RAV4 Hybrid and Highlander Hybrid.
In those vehicles, the rear wheels are driven solely by a single electric motor-generator, which receives power from the onboard hybrid battery. There's no mechanical connection between the front and the rear wheels, and when extra traction isn't required, the rear axle is disengaged (except on deceleration, when the rear wheels capture momentum through the motor-generator to recharge the battery).
Finally, there's the Toyota Prius and its simpler AWDe system. As one might expect, this Toyota all-wheel-drive setup is designed to maximize fuel efficiency and minimize weight and drag. As such, the rear motor is an induction-type unit that's only available at speeds below 43 mph. Like the system in the RAV4 and Highlander Hybrids, there's no transfer case and no mechanical connection between the engine and the rear wheels.
Somewhat surprisingly, AWDe always provides motive force at speeds below 6 mph, even in dry conditions. That's likely because the electric motors operate more efficiently than the gasoline engine at low speeds, helping reduce emissions and fuel consumption. If the system detects wheelslip above 6 mph, it will continue sending electricity to the rear motor until the Prius exceeds 43 mph. Predictably, the all-wheel-drive Prius is no off-roader or rally warrior—if you regularly plan on blasting your Toyota across the snowy landscape at high speed, get one of the other vehicles on this list. (Also, get your head examined and slow down, ya loon!)
Toyota All-Wheel-Drive Proliferation
Thanks to the Camry and Avalon, Toyota now offers all-wheel drive on most of its model lines (curiously, those sedans received four driven wheels before the C-HR crossover did). And while we auto enthusiasts are quick to suggest dedicated winter tires alongside (or even in lieu of) all-wheel drive, there's no denying the benefit the systems add in some off-road situations and unpleasant weather.
Nevertheless, we remain impressed at the diversity of purpose found in the Toyota all-wheel-drive lineup, from the simple and cheap Dynamic Torque Control to the sophisticated Dynamic Torque Vectoring, to say nothing of the unusual and efficient hybrid systems. Now, about that rally-ready RAV4 All-Trac