Continuously variable transmissions have been one of the most polarizing automotive transmission technologies ever since their inception. The idea that near infinit gear ratios could be achieved for an Internal Combustion Engine seemed unfathomable decades ago, but now that automatic transmissions have exploded in popularity, the lackluster CVT experience put it in a secondary place. They’re not able to handle large amounts of torque. However, Nissan figured out a way past this problem for high-output rear-wheel drive applications in the late 1990s. Nissan used a toroidal “gearing” system to double the amount of parts in a CVT.
Jason Fenske from Engineering Explained breaks it down in his latest video. Nissan’s continuously variable transmission from the Y34-generation Cedric used a toroidal-type layout rather than a belt-driven one, which you may be more familiar with. Toroidal CVTs use a combination of discs and power rollers attached to the input shaft to adjust gear ratios, which Fenske breaks down in the first part of the video below. Usually for toroidal CVTs, there’s one input disc, and one output disc to handle all the torque coming through the engine. In order to overcome the transmission slipping from too much torque, Nissan simply added another set of toroidal pieces, essentially splitting the work the transmission has to do in half. That means Nissan can push more torque through the transmission without worrying about slippage. The company claims this gearbox can withstand 10 tons of forced being pushed through it, which is a lot.
Perhaps even cooler is the specialized lubricant that Nissan developed that’s able to fit between the toroidal CVT internals while still being able to transmit power. Its molecules are actually shaped to lock together when compressed so that the power roller and discs can still transfer force, even when there’s a lubricant in between them. This immensely unique CVT setup can be quite expensive to build however Nissan is expecting R&D costs to go down as the technology becomes more popular. So this super efficient and reliable transmission still has hope to regain its standings in the brutal automotive market. Or does it?