In February this year, we reported on a little-noticed trade show exhibit where Jaguar Land Rover (JLR) displayed a prototype transmission system. Now, in a flurry of technical announcements taking in electronics as well as new Ingenium engine variants, the luxury sports car and SUV manufacturer has confirmed the existence of the transmission program and has revealed more detail surrounding the aims behind the project and the thinking that led the company to choose the DCT approach.

Between the Aachen Colloquium last autumn and this September’s technology announcement, the Polar 3 project has morphed into Transcend and has taken on the status of an advanced research program, though no completion schedule or target applications have been disclosed. Instead, Transcend is presented as part of a package of technologies that promise to improve performance by up to 25 percent and reduce fuel consumption by up to 15 percent.

Of this 15 percent economy improvement, the Transcend transmission alone is claimed to account for nearly 10 percent – and, says JLR, it does this while delivering “new levels of off-road performance.”

Nick Rogers, JLR Group Engineering Director, commented in a media release: “Environmental innovation is at the heart of our strategy to dramatically reduce emissions up to 2020 and beyond. With the Ingenium family of powertrains and advanced research projects such as Transcend, future Jaguar Land Rover vehicles will emit significantly less CO₂. By 2020, new technologies will help us reduce our CO₂ emissions by a further 25 percent.”

More specifically, the company claims that Transcend will “improve the driving experience and environmental performance of our vehicles,” and that it will also “make maneuvering and off-road use easier than ever before for drivers whilst also improving on-road vehicle dynamics and CO2 emissions.”

These are pretty weighty claims for a single component such as a transmission, which after all is no more than a device which transmits torque from the engine to the road wheels. In particular, why would a dual clutch transmission – a gearbox type which to date has never been deployed in a premium off-rad vehicle – offer such advantages over a sophisticated eight-speed planetary automatic such as the ZF, which by common consent represents the state of the art in transmission design?

For answers to these key questions we turned to the brains behind the innovation – Jaguar Land Rover engineer Steve Nesbitt, co-inventor of the Transcend concept and now the senior manager of the program. Asked whether Transcend is being developed primarily for off-road use, Nesbitt conceded that while the concept does have the massive advantage of allowing seamless transition from an on-road to off-road environment, and back again, without the need for the driver to adjust which transfer case ratio (high range or low range) they need to be in, it does also “enable an increase in vehicle composure” on-road, when towing, during low speed parking or creeping maneuvers such parking on gradients and hitching a trailer. It also enhances vehicle pull-away at altitude, he says.

Yet the motivation for the initiative has little to do with any shortcomings of modern planetary ATs. Instead, it revolves around packaging space and vehicle mass. “Current transmissions are class leading for their type and classification,” says Nesbitt, “but growing demands for electrification and improved vehicle performance, functionality and feature mean we have a lot of competition for available package space within the vehicle. Transcend offers the opportunity to integrate several features and functions, previously delivered by separate units, into one, which enables a package and weight benefit in doing so.”

The current program focuses on large SUV applications and, for these, the Transcend concept is 20 kg lighter than a conventional automatic transmission and transfer case. The package length benefits vary depending on the engine, vehicle and type of application, but nominally Transcend is 50 to 70 mm shorter than the transmission and transfer case combination.

“The ultra-wide ratio capability and ratio flexibility of Transcend also means we can enable a better combination of performance and economy, rather than biasing to one or the other,” adds Nesbitt.

In effect, the Transcend unit does the job of the eight-speed ZF AT and two-speed transfer case combination. But there is more, as Nesbitt explains: “In essence, Transcend can do everything these two transmissions can do in combination, and more. The use of a dual clutch module means we can directly control the torque input to the transmission itself, and, in conjunction with the ultra-wide ratio gearing, deliver exactly the required amount when needed.”

A conventional automatic transmission can also do this, but only when the torque converter is locked, he warns. One of the benefits of the Transcend concept is to enable a better level of driving composure and to assist in minimizing unnecessary amounts of wheel slip on all on- and off-road surfaces.

Transcend uses four clutches in total, with no torque converter. One clutch is used to disconnect the engine, to enable electric-only driving for specific applications; the second controls the all-wheel drive torque distribution (the center differential function). The two clutches within the DCT module are used to launch the vehicle from rest, in all circumstances, and to enable uninterrupted torque transfer during gear shifting. All four are multi-plate wet clutches, notes Nesbitt, and each is optimized in terms of its materials, design and size for each of the four functions.

Ratio span of 20 is the industry’s highest

With this level of complexity, efficiency might be expected to become a concern – but Nesbitt is swift to allay any such fears. “Efficiency is a complex matter,” he says. “There are several key factors which influence this. Transcend uses fewer multi-plate wet clutches than a planetary automatic, and does not have a torque converter. It does use an active pump and hydraulics system to minimize losses and, by virtue of the gear train architecture we are developing, it will have lower parasitic losses.”

The exceptionally wide ratio span of 20 does of course give the Transcend concept its most headline-grabbing advantage, that of eliminating the transfer box so that drivers can proceed seamlessly from off-road conditions to a paved highway. But there are other big benefits, too, as Nesbitt explains: “The wide ratio capability also means we can protect the clutches during hard and arduous use, which is one factor that has prevented DCTs becoming adopted in full-sized SUVs – though they are currently being adopted in crossover vehicles.”

“I have already listed a number of examples where the ratio spread of 20 can benefit a vehicle on road,” he adds. “These are relevant to larger all-wheel drive vehicles, and some are relevant to other vehicle segments in terms of function and performance benefits.”

One complaint that has troubled some luxury-car DCT applications is that of poor shift quality and drivability, especially at low speeds. But, again, Nesbitt has an answer: “Jaguar Land Rover already have a proof of concept vehicle running, which has confirmed that we can match the shift quality attributes of conventional automatic transmissions. It is hugely important that we offer our customers the refinement and luxurious experience they would expect from either a Jaguar or Land Rover.”

For the moment, Transcend is a dedicated in-line architecture, or North-South as Jaguar Land Rover refers to it. It is configurable to be all-wheel drive, torque-on-demand or rear-wheel drive, but always for an in-line installation. “It is not configured for a transverse, or East-West installation,” he stresses.

With Transcend still being very much a research project, the full application set has not yet been defined. Nesbitt is understandably not keen on disclosing any torque capacities or even hinting at which vehicles – including the new Defender – might be in the running to take the unit. “This is an advanced hybrid transmission research and development program and is still subject to ongoing tests and further development,” he reiterates, “so we are not putting any timescales on when this will come into product or which vehicles it will appear on.”