If you’re a vocational truck driver, you know how hard it can be to navigate a tight jobsite on a good day – and the nightmare it becomes when it rains, or if there’s a fresh gravel surface.
With the introduction of its 2017 powertrain, Mack Trucks is providing owners and drivers with new tools to handle those low-speed jobs. New 13- and 14-speed mDRIVE automated manual transmission options include one or two low-speed creeper gears that make moving heavy loads or climbing slopes far smoother, especially when paired with the company’s updated engines.
I had the opportunity to give the new tools a test drive at Mack’s customer centre in Pennsylvania in September. It was a good chance to explore the capabilities of Mack’s new powertrain in real-world situations, both on highway and in tight quarters.
An off-road track that featured muddy stretches, loose gravel of various sizes, and several steep grades tested the mettle of the updated equipment fitted on a Mack Granite dump truck. The truck, loaded to about 70,000 pounds, was equipped with the 445-hp MP8 engine and 14-speed mDRIVE transmission.
Creeper gears power up slopes
The MP8 provided plenty of power to haul the truck up grades and keep up speed through each challenging road surface. At lower speeds, the mDRIVE kept the truck responsive to the throttle. Hills always make me nervous in vehicles with manual transmissions, but Mack’s Grade Gripper helped handle slopes with ease – let off the brakes, and the truck stays where it is for three seconds, which is plenty of time to put power to the engine.
Using the simple push-button gear selector on the dash, I shifted the truck into the lowest creeper gear – which boasts a 32:1 ratio – and hit the throttle. The engine easily held the rpm needed to climb the grade, even on a surface still slightly slick after an early rainfall. Then we turned around and repeated the test – in reverse. The Granite hardly paused in reversing up the slope. It was an impressive example of keeping power and torque on the ground in tough conditions. Tim Wrinkle, Mack Construction Product Manager, said the new creeper gears give vocational trucks new flexibility for owners.
“The further reduction gears allow us to spec out these trucks almost as two trucks in one,” he said. “You can use a different rear axle ratio that provides better fuel efficiency when you have to get the load somewhere; then you have lower gears that allow you to work at low speeds on the jobsite.”
I also drove several other trucks, including a Granite roll-off refuse truck, a Titan pulling a flatbed trailer, and a Pinnacle on-highway tractor-trailer. In each truck, the low-speed maneuverability was the focus of the demonstration, whether for easing around tight corners or backing through obstacles on a small simulated jobsite. Paired with updated MP series engines, the mDRIVE handled each situation with ease.
Scott Barraclough, Mack Technology Product Manager, explained: “We have had the 12-speed mDRIVE since 2010, and to complement that we are adding 13- and 14-speed options which will help our vocational customers and those hauling heavier loads. The 13-speed has a single creeper gear, which offers low reduction for increased startability and jobsite maneuverability. The 14-speed has two creeper gears, one of which is an ultralow- reduction 32:1 gear for very low speed operations. We’re also offering multiple-speed reverse, with up to four reverse gears.”
Mack announced in May that with the success of the mDRIVE 13-speed, the company will make it standard on the Granite model.
Greater power and efficiency
The MP7 and MP8 engines have both been updated to meet 2017 emissions standards, and both boast improved power and fuel efficiency, related Roy Horton, Mack Director, Product Strategy.
“When we look at this hardware, all of the areas bring benefits to our customers,” said Horton. “Common rail fuel injection brings fuel economy improvements; our patented wave piston also adds fuel economy; shimless rockers and two-piece valve covers bring reduced service times and simplify the service process, and the assembled camshaft and reduced cylinder block weight [in the MP8] reduce weight in the engine.”
The MP7 now offers 425 hp, up from its previous 405 hp, giving it what Horton referred to as 13-litre performance in an 11-litre engine. For weightconscious customers, that means a 400-pound reduction in weight. Horton said the engine provides a 2.1 to 5.1 percent improvement in fuel economy.
On the MP8, a similar increase in fuel economy accompanies improved power and torque.
“The 445- and 505-hp ratings come with 1,860 pound-feet of torque; we’ve updated the power and torque curve, along with meeting emissions regulations and improving fuel economy 2.5 to 5 percent,” Horton said.
Mack will offer optional turbo compounding on the MP8. The unit captures waste energy and returns it to the crankshaft, where it is used to increase fuel economy even more, by 8.1 to 8.8 percent compared to a 2014 baseline, Horton said.
Updated exhaust aftertreatment is also going to be available. The ClearTech One aftertreatment is now a single unit, which results in less space being used for emissions and more flexibility for body builders.
“The one-box system saves weight and space on the side of the rail; we’re able to save about 11 inches of packaging,” Wrinkle said. “That’s important for construction vehicles, as it makes it easier to package the body and build what owners need.”
