Automatic transmissions gaining ground

With engines and transmissions sharing more data, Automated manual transmissions continue to make inroads in trucking, and AMTs now are being spec’d on a significant share of new trucks for reasons including fuel economy and easier driver training.

The trend is likely to continue.

Two types of automatic transmissions are available for heavy-duty trucks: Automated manual transmissions and automatic transmissions. 

Both are two-pedal designs. Most drivers probably would be hard-pressed to tell much of a difference between them in real-world driving situations.

The basic difference is that automated manuals are manual gearboxes, with all the clutch actuation and gearshifts handled by electronically controlled systems. A true automatic transmission “for a Class 8 truck is usually fully automatic, like a typical car transmission, with planetary gearing with several multi-disc packs for clutches,” Ed Saxman, product marketing manager with Volvo Trucks North America, told our sister site, CCJ. These transmissions have a torque converter to enable powershifts of the planetary epicyclic gearing units that provide the various gear ratios.

Steve Rutherford, powertrain marketing manager for Caterpillar OEM Solutions Group says the advantages of a pure automatic design are a perfect fit for the company’s vocational truck line, adding that both transmissions work well in specific applications.

“Both types of transmissions have two pedals and a shift pad instead of a gearshift lever,” Rutherford says. “It took a lot of work to perfect automated manuals to engage a dry clutch and generate well-synchronized shifts. What they’ve done with those products is amazing.”

But many drivers – particularly the veteran ones – feel that automatic transmissions somehow detract from the skill set they’ve honed over decades.

“I’m a truck driver, not a steering wheel holder,” Carl Ciprian, a driver with Fayette, Ala.-based N&N Transport, says. Ciprian never has driven an AMT and says he never will, preferring to stick with an Eaton-Fuller 18-speed manual gearbox.

“I can understand why fleets like AMTs,” he says. “It’s all about fuel economy.”

More on automatic transmissions: Will drivers come around?

But fleets are gravitating toward automatic transmissions – and in surprisingly high numbers. David McKenna, director of powertrain sales for Mack Trucks, says its mDrive is being spec’ed in about 38 percent of Pinnacle tractors, similar to the 35 percent to low 40 percent range that other manufacturers report.

Saxman told CCJ more than 50 percent of all new Volvos sold this year have been spec’d with the company’s I-Shift AMT.

For more on the transformation taking place in the gearbox, click here