Acceptance of AMTs Grows, Makers Say

This story appears in the March 25 print edition of Transport Topics.

The hottest trend in heavy-duty truck transmissions — the growing acceptance of automated manual models — not only takes most of the shifting worries out of drivers’ hands but also integrates with other operating systems such as cruise control and engine brakes to make operations safer, easier and more fuel-efficient, according to manufacturers.

An added benefit of automated manual transmissions is that they could help alleviate driver shortages, a manufacturer said.

Automated manuals — also called automated mechanicals — can be shifted either manually, but without a clutch pedal, or automatically. For manual mode, manufacturers have placed mechanisms within reach of the driver, allowing the trucker to switch gears as warranted. This compares with automatics, which take the choice of gears completely out of drivers’ hands.

Tom Stover, Eaton Corp.’s chief technology officer for the company’s vehicle group, told attendees at American Trucking Associations’ recent Technology & Maintenance Council meeting, “The era of allowing unrestricted decisions about gear shifting is probably coming to an end.”

With shifting and clutching automated, it’s possible for AMTs to offer more gears than standard manual transmissions. The result of moving to 10- and 12-speed models with close ratios is faster acceleration, better fuel economy and reduced damage to the clutch, manufacturers said.

“An automated transmission can help find the engine’s sweet spot,” said Jeff Seger, executive director for Cummins Inc.’s engine controls systems, who also spoke at the TMC meeting.

He said the current driving trend is “downspeeding” the engine, which can reduce the cruising speed and provide a 1% fuel-economy gain for every 100-rpm drop in engine cruising speed.

Stover concurred. Down-speeding requires more frequent shifts to keep an engine running in the sweet spot, he said. That “puts a premium on the transmission to keep the vehicle drivable.”

“Automated transmissions are enablers for downspeeding, and it helps with shift performance” because they can make fast shifts and smooth shifts, Stover said, adding, “Automated transmissions put a restraint on driver behavior, increasing efficiency.”

As for safety, he said AMTs “allow drivers to pay more attention to the road [and] take some of the overhead out of the truck driving business.”

Martin Daum, CEO of Daimler Trucks North America, has said that AMTs could help solve driver-shortage concerns because new drivers wouldn’t have to master changing gears using a clutch pedal. He said that AMTs enable average drivers to be as productive as a carrier’s best drivers.

Daum also said that he expects AMTs to continue gaining market share.

According to DTNA, AMTs made up about 25% of Class 8 market share in 2012. The company predicts that share will grow to about 55% by 2016.

But while AMTs appear to be gaining in popularity, other transmission types are still produced and purchased.

Allison Transmission Inc. has introduced a fully automatic transmission 10-speed that offers full-power shifts and clutchless starts, with enough ratios to supply on-highway fuel economy and performance, the company said.

Steve Spurlin, Allison’s executive director of global application engineering and vehicle integration, said the new heavy-duty fully automatic transmission, the TC10 TS, “is engineered specifically to provide the benefits of continuous, uninterrupted power to the Class 8 tractor market.”

The design incorporates twin countershafts in a conventional main box and “a 2-speed planetary range output section for higher average vehicle speeds. It also features helical gears for quieter operation,” Spurlin said.

He said the transmission includes electronic controls that provide enhanced acceleration control “to allow for an even greater ability to improve fuel economy by moderating aggressive driving practices.”

And on Feb. 28, Eaton Corp. announced that it would launch a new manual transmission this year.

The line will be called the Fuller Advantage Series, said Jeff Walker, global product director for manual transmissions.

“Many of the design upgrades and changes we’ve made are the direct result of customer input,” he said. “Much of the efficiency gained is the result of our new dry sump technology that allows for precise and efficient lubrication. We also eliminated the transmission cooling system, which reduces the weight of the unit and improves maintenance.”

AMTs have earned the respect of several truck manufacturers.

Europe embraced automated technology in part because a gearbox that is shifted by a computer no longer needs the synchronizers used for standard lever shifts. By eliminating the synchronizers, manufacturers can build smaller, lighter gearboxes that eliminate the need for repairs to the synchronizers.

Drivetrain maker Detroit Diesel Corp., along with truck makers Volvo Trucks and Mack Trucks, have introduced their own AMTs, which use a single countershaft and aluminum case to reduce weight, to the North American market.

Brad Williamson, manager of engine and component marketing at DTNA, which owns the Detroit brand, said, “The Detroit DT12 is a heavy-duty 12-speed automated manual transmission available in direct or overdrive. [It] uses a pneumatically controlled clutch to shift.”

Mating a proprietary engine and transmission makes shifting “extremely smooth” and efficient, Williamson said, because “load and grade sensors will select the appropriate start gear, and the DT12 can skip unnecessary gears to reach cruise speed faster and more efficiently.”

Williamson said the new transmission allows the driver to choose shifting regimens designed for either fuel economy or performance, or to control the shifts manually. He said the fuel-economy driving mode “uses many of the DT12’s features — skip-shift, optimized shift strategy, eCoast, etc. — to deliver outstanding fuel economy.”

DTNA, based in Portland, Ore., makes Freightliner and Western Star trucks.

Ed Saxman, drivetrain marketing product manager at Volvo Trucks, told TT that his company’s I-Shift can be ordered with several premium software packages, which provide some unusual functions that are especially useful in vocational and heavy-haul situations.

One feature is the Engine Brake Performance Mode, which is integrated with the cruise control and the transmission, Saxman said. The cruise control stalk allows the driver to set the brake for performance mode, causing the transmission to shift automatically and continually to the lowest usable gear to provide the highest level of braking. The driver also can set a brake cruise speed, causing the brake to function through the cruise control to maintain the vehicle’s speed on a long downgrade and modulating the level of braking and shifting gears.

Volvo recently introduced the XE concept, consisting of a 12-speed I-shift and a 2.64:1 rear-axle ratio that, with engine torque enhancement, allows a low 1,150-rpm cruise at 65 mph and provides a fuel savings of about 3%.

Mack Trucks offers a similar concept to Volvo’s XE called Super Econodyne, which is included in its mDrive AMT. The Super Econodyne is adapted to Mack’s different torque and power curves through an altered shift algorithm.

Such “downspeeding” drivetrains would be impractical without an automated gearbox to take over downshifting duties for the driver because the low cruise rpm necessitates an earlier downshift when climbing some grades, a Mack spokesman said.

David McKenna, director of Mack Powertrain sales and marketing, reported on the availability of an enhancement that helps drivers shift manual transmissions with the precision of an automated gearbox.

“Mack recently released our Electronic Progressive Shift program for customers choosing manual transmissions,” McKenna said. “This is a unique technology because existing Progressive Shift programs use fixed engine rpms in each gear to limit excessively high rpms between shifts. This can limit the acceleration rate up highway on-ramps and even through simple intersections.

“With Mack EPS, we rely on the torque output versus the torque required, which then flattens out the acceleration rate so it does not vary so much with the conditions,” McKenna said. “This means that, when power and rpm are required, the driver gets what he needs and not a fixed amount.”

The system, McKenna added, gradually ramps down the torque when the shift rpm is reached, making it “much smoother and easier on the drivetrain and load.”

The unit “looks at more than 30 streams of data,” McKenna said, including whether the vehicle is ascending or descending a grade or running on a level road before making a shift decision.

Although Eaton recently unveiled a new manual transmission, the company also offers an upgraded, automated UltraShift Plus, which is available in 10, 11, 13 and 18 speeds with direct and overdrive models, said Shane Groner, North America product planning manager for Eaton’s Commercial Vehicle Transmission Division.

Offering more ratios for the automation to choose from can optimize operating rpm and save fuel, he said.

“There are thousands of UltraShift Plus transmission configurations available, so fleets are not forced to compromise,” Groner said. “Other advantages include built-in features, like Hill Start Aid, which prevents rolling back when stopped on a grade and provides the driver with a consistent, controlled launch.”

Low-speed maneuverability is enhanced through gear logic and extended low- and reverse-ratio coverage. This feature allows the driver to creep at less than 1 foot per second in an appropriately spec’d truck, he explained.

Bruce Harmon, managing editor of Transport Topics Magazines, contributed to this report.