Elvin Knollman grew up on a beef-cattle farm in southeastern Indiana, and helped his family keep machinery running. He still lives in the area, near Greensburg, and manages Trans Mark Logistics, a small fleet of tankers that haul gasoline, jet and diesel fuel, and other petroleum products in the Hoosier state and surrounding areas. He has 10 power units driven by hired hands and three more owner-operated trucks, including one run by a son.

His background gave him mechanical ability and a bent toward finding better ways to accomplish things. That and his own experience as a driver led him to try Mack’s then-new mDrive automated manual transmission in 2011. He thought the promise of easy operation and greater efficiency made sense. It was so successful that he ordered more as he replaced old equipment with new tractors. Most of them now have the AMT. “Only two still have manuals, and one of those is a spare,” he says.

Compared with his manual gearboxes, the mDrive tractors began turning in better fuel economy, about a quarter to a half a mile-per-gallon more. But that’s not all.

“I can see at the end of a day that the drivers who drove the automatics weren’t as worn out as the ones who drove manuals,” he said. “Thinking about shifting all day mentally wears you out.” As for reliability, “I haven’t had any issues with it at all.”

Knollman is among a growing number of American fleet operators who are swinging to automated and automatic transmissions for their heavy trucks and tractors, just as operators of most medium-duty trucks did years before. In 2005, self-shifters were in about 10% of Class 8 trucks, and now it’s far higher.

Builders see growth

“Penetration of the mDrive automated manual transmission in our Pinnacle models is now over 70%, and we’re seeing strong growth for our heavy-duty AMT, the mDrive HD, used in vocational applications,” says Stu Russoli, highway and powertrain products marketing manager at Mack Trucks. Recently announced 13- and 14-speed versions of the HD, with two extra ratios for better startability, are expected to increase interest among vocational operators.

Russoli says customers use the mDrive to boost their fuel efficiency and productivity, without impacting performance. “Because the mDrive is fully integrated with our MP series engines, it’s able to use the data it monitors — speed, weight, torque demand and more — to get the best performance and efficiency from the engine in any situation.”

The mDrive is Mack’s adaptation of the I-Shift from Volvo, its sister company, where the automated product is standard on all VN and VHD models (as mDrive is on many Mack models).

“Currently, more than eight out of 10 Volvo trucks sold in North America are equipped with the I-Shift, and we continue to see that number grow,” says Allison Athey, Volvo product marketing manager — transmissions. “The I-Shift is more popular with our on-highway customers, but we are seeing growing interest on the vocational side, thanks in part to the I-Shift for Severe Duty.” That’s a reinforced version of the I-Shift engineered to handle the heavier loads and more frequent shifting found in vocational and rugged operations.

At Daimler Trucks North America, about half of Class 8 on-highway units are being delivered with automated manual transmissions, according ti Kelly Gedert, manager, powertrain marketing.

“Both on-highway and vocational segments continue to experience year-over-year growth in transmission automaticity. We anticipate seeing an ongoing trend of more fleets adopting AMTs as they realize benefits for both newer and more experienced drivers, such as ease of operation, enhanced fuel economy and safety.”

At a briefing with reporters last October, DTNA officials noted that 22% of Class 8 Freightliner and Western Stars in the U.S. and Canada were being spec’d with the company’s own automated Detroit DT12 transmission, and that penetration was 41% in the Cascadia.

Still a market for manuals

At International, automated penetration in Class 8 is less — 33% automated and automatic and 66% manual, according to Steve Gilligan, vice president, product marketing.

“Though the majority of sales of on-highway tractors continues to be manual transmissions, the recent driver shortage has driven many more customers to spec transmissions that are more driver friendly than that of the typical manual transmissions.” For that reason and for improved fuel economy, he says, “in keeping with our open integration approach, International offers both the Allison TC-10 Automatic and Eaton Advantage Automated transmissions.”

It’s similar at Kenworth. In 2015, customers purchasing new Kenworth Class 8 trucks specified manual transmissions at a 59% rate followed by automated (34%) and automatic (7%), according to Marketing Director Kurt Swihart. “For our Kenworth T680 on-highway flagship truck, the breakout was split 50-50 between automated and manual. For our T880 vocational flagship truck, manual transmissions were at 55%, followed by automated (30%) and automatic (15%).”

At Western Star, nearly 70% of vocational trucks now go out the door with Allison automatics and a few more percent get Eaton automated transmissions. Akbar Gous, national accounts manager, says because Allisons have been around longer, they are trusted more. Most Western Star highway trucks, however, still are equipped with manual gearboxes.

Automatics

At Allison, which offers full automatic transmissions, sales to the on-highway market amount to 53% of its North American business, says Craig Coven, manager, communications and media relations. The company doesn’t break down sales by application, but for many years Allison has all but owned the market in heavy trash-collection trucks, and they’re becoming more popular in heavy construction trucks. At one time Allisons went into nine out of 10 medium-duty trucks engaged in beverage and food deliveries, and freight pick-up and delivery, but proprietary transmissions have cut into market share.

In recent years Allison has concentrated on improving fuel economy by developing a series of Fuel Sense refinements, like changing into neutral at stops and optimal shifting based on what its electronic controls observe from operational patterns and drivers’ habits.

International’s Gilligan said 88% of its Class 5 through 7 midrange trucks get automatics, mostly Allisons, and now Eaton’s recently released Procision 7-speed dual-clutch transmission. Eaton calls it an automatic. Although it sends continuous power to the driveline, it has no torque converter, so it feels more like an automated gearbox.   

Eaton

Eaton makes many of the Class 8 automated transmissions and nearly all manuals for North America. The automated take among all heavy truck customers now averages 50%, up from 20% in 2009, says Ryan Trzybinski, product strategy manager for commercial powertrains.

Eaton has expanded its Smart Advantage automated offerings with the Cummins ISX15, and the lightweight gearbox is also teamed with Navistar 13-liter diesels and with Paccar 13-liters in Peterbilt and Kenworth trucks. Eaton Smart Advantage 10-speeds now account for about half of Eaton’s automated production. The others are the UltraShift Plus models that have been considerably refined in recent years.

The 10-speed manual is still the most common type for freight-hauling highway rigs. Thirteen-, 16- and 18-speed gearboxes remain popular among owner-operators and “premium” fleets. These are usually used with “big power” engines — generally 475 to 500 hp and more. Trzybinski says that “performance” market will always exist, as will the manual market in general; time will tell at what level.

Heavy trucks employed in construction and certain other vocations tend to have 11-speed “low-low” manual transmissions with three ratio ranges. Eaton makes automated versions of these and the multi-speed transmissions, so customers can choose to go shiftless or do it themselves.