Mack Trucks released 13- and 14-speed versions of its Mack mDrive HD automated manual transmission to meet a wider range of customer applications, the company announced at the NTEA Work Truck Show.

Available in direct or overdrive configurations, the mDrive HD 13-speed offers a low reduction gear ratio designed for easier starting on steep grades or when the truck is under heavy load.

The mDrive HD 14-speed, available only in an overdrive configuration, adds a second ultra-low-speed reduction gear designed for curb pouring applications or low-speed, heavy-haul maneuvering. Both transmissions offer up to four reverse gear ratios.

“We launched the original mDrive HD in response to customers looking for an AMT capable of withstanding tough vocational applications,” said John Walsh, Mack vice president of marketing. “Now, with the mDrive HD 13- and 14-speeds, we’re taking the next step and combining low-speed capabilities with the performance and productivity benefits of our ground-breaking AMT.”

The new mDrive HD transmissions share architecture with the standard mDrive HD, including reinforced internal components and the same gear ratios for the 12 forward speeds.

The addition of the low reduction and multispeed reverse gears is made possible by a short extension added to the front of the transmission case. The new mDrive HD models are less than five inches longer and 90 pounds heavier than the standard mDrive HD.

Customers will also now have the option to spec the mDrive HD in Mack Pinnacle models, including the two new transmission options. In addition to off-road, heavy-haul and construction applications, the new transmissions’ use of a faster rear axle ratio can improve on-road fuel economy while maintaining startability.

“The mDrive HD is just as at home on the highway as it is on the job site,” said Stu Russoli, Mack highway and powertrain products marketing manager. “Highway customers with challenging loads will appreciate the extra flexibility provided by the low reduction gear ratios.”

All Mack mDrive transmissions, including the standard mDrive and mDrive HD, also received numerous updates for improved performance and durability. The transmissions are controlled by a redesigned gearbox control unit, while a new clutch with a larger torsional damper helps reduce driveline vibration. Component wear monitors were also added to enable predictive maintenance.

The mDrive updates also included several improvements to power take-off controls, including new main cab harnesses for all mDrive models, a reinforced range housing to handle higher PTO bending torque and an all-new cab-mounted Body Builder Module. The Body Builder Module is customizable, with user-configured software parameters to control engine speed and block reverse gears when the PTO is engaged. In addition, dual PTOs are now supported.

The Mack mDrive HD 13- and 14-speed AMTs will be available for order in August on Mack Pinnacle, Granite and Titan by Mack models.