MONTREAL, Que. –Life is full of ups and downs. Transmission makers have noticed it and now offer automated or automatic transmissions that have a “grade-sensing” feature, allowing for better vehicle performance and, in some instances, fuel savings.

Just like human drivers do with a manual, some of today’s automated and automatic trannies also “think” about the way they work when climbing or going down a hill and adapt their shifting accordingly.

Volvo has been a pioneer in that field, when it launched its I-Shift automated transmission in North America early in 2007 (it was available in Europe since 2002). At the time, we wrote about the I-Shift: “It even evaluates the level of slope of the road. It allows it to predict, 30 seconds in advance, the way the engine and the transmission will need to interact.”

A few weeks ago, Ed Saxman, product manager -drivetrain for Volvo Trucks North America, added: “Repetitive calculations continually update the microprocessor that decides whether to shift, up or down, and how many steps to take (our transmission ‘skip-shifts with abandon’). In fact, we popularized automated transmissions that ‘skip-shift’ when appropriate.”

Saxman doesn’t give any precise figures but confirms a “difference in fuel mileage.”

From buses to trucks

Volvo is no longer alone. All the buses owned by the the Societe de transport de Montreal (STM) that are of model year 2001 or newer are equipped with ZF’s automatic transmissions. And just recently, ZF offered a new software recalibration called Topodyn that includes a grade-sensing characteristic. During an interview with Truck News, Pascal Octeau, chief engineer, buses, at the STM, told us that the new feature had worked wonders: up to 20% fuel economy improvements on regular buses and up to 10% on larger articulated buses. All these fuel savings (more than $8,000 per year on a regular bus) cost just $1,000 in the investment for the software adjustment. This adds to expected lower maintenance costs, as the equipment works in its optimum range more often, and reduced emissions as well.

The good news is that the same technology could soon be applied to trucks, as explains Bryan Johnson, spokesperson for ZF.

“The transmissions that utilize Topodyn can be used in certain truck applications, but our focus has been on the bus market up till now,” he says.

Allison’s reply

Allison also recently entered the “grade-sensing club,” when it launched its LBSS (Load-Based Shift Scheduling) transmission a few months ago. Similar to ZF’s approach, this is a new software calibration, available on all automatic transmissions of the series 1000, 2000, 3000 and 4000, says Jean-Francois Aussillou, account manager -eastern Canada, for Allison Transmission.

These transmissions already had push buttons that allowed the driver to switch from Economy to Performance mode or the opposite. Now, the LBSS decides by itself when it’s time to switch from one mode to another, taking into account factors such as acceleration, the load carried as well as the slope that the truck is climbing or descending.

“If a truck climbs a hill, its acceleration is naturally slower. So the LBSS system allows a higher RPM to get more power,” explains Aussillou, adding, “at the opposite, when the truck goes downhill, the truck accelerates more quickly. In this situation, the LBSS makes sure that gears are changed sooner, in order to reduce RPM.”

Allison claims that the LBSS (available for medium-and heavy-duty trucks) can lower fuel consumption by up to 5%. And interestingly enough, the new device, standard on the new Allison transmission models mentioned above, has no impact on the ticket price.

“It’s our policy at Allison to think that we have the responsibility to offer our customers the best fuel economy, whenever we can,” says Aussillou. He adds that some truck makers might decide to charge more to customers who spec’ the new tranny, but he feels that even if it were the case, the impact would not be substantial.

Eaton climbs aboard

You might have read previous Truck News reviews of the new Eaton automated transmission called UltraShift Plus. And guess what, yep, it has a grade-sensing feature! In his article, author Paul Hartley referred to the “newly-added inclinometer, a device that measures road grade, and good software programming.”

We got in touch with Michael Holahan, manager of program management for Eaton, and asked how this new feature helped with fuel economy. Here’s what he told Truck News: “The grade sensor alone does little to aid with fuel economy. Instead, it enables superior performance and also helps with engine optimization in the shift decisions. But nothing we have seen so far would indicate that the sensor is contributing to significant fuel savings. We have seen cases where others have attributed fuel savings advantages to grade-sensing technology, but I would expect this to occur under the most highly of engineered routes and not representative of any real-life applications.”

Commenting on the results seen on the ZF Topodyn-equipped Montreal buses, Holahan says: “A good question would be to ask what they started with. If the original transmission had a ‘hard code,’ only switching from one gear to the next, adding more flexibility with a more comprehensive software might explain this big gap in fuel economy.”

He makes this comparison: “If you were to compare the first generation of AutoShift three-pedal automated transmission with the latest version of the UltraShift Plus, you’d probably also see significant improvements in performance and fuel economy as well.”

This might explain why Allison, with its new LBSS, is quite conservative with fuel economy figures, saying that it can save “up to” 5%, not more. In other words, the transmission was already quite fuel-efficient.

“The grade-sensing system alone does little for fuel economy. It’s part of an elaborate system but doesn’t do all the work. It’s a little like shoe laces. When you go out to buy shoes, you don’t concentrate on the laces, other stuff could tie them, Velcro for example, you concentrate on the performance the shoes themselves can allow you to achieve,” concludes Eaton’s Holahan.