The drivetrain of a medium-duty (Class 3-7) truck is asked to do an awful lot. It must support a myriad of missions — and there are far more medium- than heavy-duty vehicle applications. It must work reliably and last long while helping deliver lower ownership costs. And it must help make the job of the operator — who is often not a professional driver — easy and comfortable.

That's a lot to ask from a batch of components that are not always even engineered together.

But with component suppliers and truck OEMs alike recognizing the growth potential of the medium-duty market, no stone is being left unturned to field more job-specific, robust, economical and performance-oriented drivetrain solutions than ever.

“Most medium-duty buyers use trucks as tools, not revenue generators,” says Bill Dougherty, manager of dealer systems & integration for International Truck and Engine Corp. “As such, they are usually not spec'd down to the wheel seal like Class 8s.

“But as these vehicles become more sophisticated to more closely match users' needs,” he continues, “the powertrain is becoming more important to spec'ing. It is crucial to understand how the various drivetrain components work with each other and the engine. We feel a systems approach will provide greater reliability and cost performance over time compared to looking only at components individually.”

Dougherty says he sees the overall medium-duty market becoming more akin to how truck lessors operate. “Leasing companies want to offer reliable, durable trucks and are less interested in individual components than what the complete vehicle can deliver.”

According to Dougherty, International is attempting to formalize all this through a process that “tries to listen, understand and deliver what the customer needs from both a product and support perspective.”

The process involves a computerized tool dubbed CEV (Customer Economic Value) that uses an in-depth questionnaire to help match specs with specific customer requirements — “instead of throwing the kitchen sink at them.”

As Dougherty sees it, “if we as an OEM can do a better job thinking of our customers' business, we can help our customers be more profitable.”

Hal Dickson, director of medium-duty sales & development at Mack, points out that just as in Class 8, “a trend of increasing importance is ensuring driver satisfaction” with medium-duty trucks.

He says that's why higher-horsepower engines and automatic transmissions are finding their way into Class 6-7 trucks.

“Drivers want a vehicle that is easy to drive in stop-and-go traffic — thus, an automatic,” says Dickson. “Owners want to have the flexibility of using various skill levels of drivers — thus, again, an automatic. And like the auto industry and Class 8 market, medium-duty is going to higher horsepower — again, per the demands of the customer.”

Another spec heavily influenced by driver choice is brakes. Since the skill level of medium-duty drivers often does not have to reach the magnitude of a Class 8 trucker, CDLs are not mandatory. However, as Dickson points out, since some states require an “air” endorsement on the driver's license or a CDL for any vehicle with air brakes, the selection of hydraulic brakes for Class 6 trucks continues to rise.

According to Paul Johnston, ArvinMeritor's senior director, North American foundation brake business, air-braked vehicles are typically more expensive to manufacture but that can be mitigated if a buyer opts to spring for air suspension.

However, he says the development of electronic braking systems (EBS), including electro-hydraulic controls coming up from the light-duty side, may eventually make air brakes “more competitive” in medium-duty trucks.

“It's easier to get EBS onto a truck where there is no air-braked trailer to deal with,” he notes. “Along those lines, we expect an electro-hydraulic control system will become standard equipment on a Class 6-7 vehicle very soon and later on lighter medium-duties.”

According to Johnston, bringing such an EBS system to medium-duty trucks would provide these key benefits:

• Better actuation timing for improved stopping distances

• Better pedal “feel” for drivers

• Lower operating costs due to fewer parts and perhaps some weight reduction.

While nearly all hydraulically braked trucks use disc brakes, Johnston says the “story is yet to be told” as to whether discs will migrate to air-braked medium-duty trucks, too. “Air brakes remain largely a customer preference because medium-duty vehicles are so cost-driven.”

While the first EBS and wider use of air brakes are in the medium-duty future, automatic and automated transmissions most definitely represent the here and now, as well as tomorrow and the day after.

Mitch Murray, manager of North American market development for Allison Transmission Div. of General Motors, says he doesn't know “if it will be in five or fifteen years, but one day all the transmissions in medium-duty trucks will be automatic or automated units.”

He says the graying of America is a factor, as is the tight driver pool in general, but he says the “main selling point is consistent performance. With an automatic you can go from 0 to 40 in half the time of a manual. On top of that, traffic density is getting worse every day.”

According to Dan Cutler, director of product development for General Motors Isuzu Commercial Truck, “automatics are being heavily adopted by medium-duty truck buyers and they dominate especially in Class 4 and 5.

Cutler says Isin and Allison automatics are now available on Isuzu and GM trucks. He reports that the future offering of an Isuzu automated manual is currently under review. If adopted, that unit would be aimed at Class 4 and 5 trucks.

Peter Tizzano, national sales manager-medium duty for Roadranger, concurs the general trend is toward greater use of automatic and automated transmissions. “It's tougher than ever for medium-duty fleets to find skilled drivers that can handle a manual transmission, and drivers in more heavily congested areas like the extra assistance”, he points out.

He calls the Eaton AutoShift six-speed automated transmission a “great medium-duty spec” and says the new UltraShift 6-speed, which he describes as a two-pedal design boasting all-automatic functioning, will soon join it in the Roadranger lineup.

“The UltraShift is aimed at Class 6-7 users,” says Tizzano “It uses the same electronics as the AutoShift but adds an automatic clutch module,” By comparison, the AutoShift requires using the clutch to start and stop.

“The UltraShift has what we call ‘urge to move’ that simulates the functioning of the torque converter to give it a response time that is instantaneous for improved driver feel,” he remarks.

According to Tizzano, the UltraShift will compete with Allison's MD automatics. “It's a well-known fact the automatic penetration of the medium-duty market is increasing and that means opportunity for automated transmissions.”

While the mighty automatic gets challenged by a new automated contender and brakes prepare for electronics, that most stalwart of components-the axle-is also getting more attention.

At least that's the contention of Tim Farney, ArvinMeritor's director of marketing for axles & drivelines.

“Over the last several years,” says Farney, “we have rolled out a whole new family of front axles and added drive axles to our medium-duty line.

“There's a greater need for more cost-efficient design, whether by using lighter-weight materials or better packaging with other components to match different vocations,” he continues.

“Our 10,000- to 12,000-lb. capacity front axles bring commercial truck design down to the lower GVW classes to provide a more robust product than a beefed-up pickup truck axle can.”

In Farney's view, medium-duty truck buyers “should not have to compromise. A medium truck's duty cycle can be just as rigorous as that of a heavy-duty truck — and with more stops and starts,” he states.

General Motors Isuzu's Cutler remarks that people buy trucks because they need them, not because they want them.

“That means OEMs have to be responsive,” he says. “They have to be willing to consider any component development that will enhance the product for the customer.”

Peter Tizzano, national sales manager-medium duty for Roadranger, suggests that when medium-duty fleet managers think of braking they should not overlook the safety benefits of an Eaton VORAD (Vehicle On-board RADar) collision-warning system.

“VORAD has been seen as a Class 8 product,” he advises, “but spreading its cost out over the life of a medium-duty vehicle, and factoring in insurance benefits a fleet may receive, could make it a cost-saver over the long term.”

According to Roadranger, the Eaton VORAD EVT-300 system helps prevent or reduce the severity of accidents by alerting a driver to hazards ahead of and alongside their truck. The system is available as a retrofit kit for most vehicles. For more information, go to www.roadranger.com.