LAS VEGAS -- Mack Trucks unveiled a heavier-duty version of its mDrive Class 8 automated manual transmission at the World of Concrete show, and executives said it will be standard on the Granite on/off-road model.

“Our construction customers told us they wanted a heavy-duty version of the mDrive designed specifically to handle rough jobs in tough conditions,” said Stephen Roy, president of Mack Trucks North American Sales and Marketing.

“We listened to them and developed a reinforced rugged transmission that will help our customers deliver power, performance, enhanced durability and improved driver satisfaction in a time when the industry is experiencing a driver shortage.”

The mDrive HD has hardened gears, synchros and main gear-dog clutches to handle the rigors of off-road running under heavy loads, Roy said. It is engineered to work exclusively with Mack MP7 and MP8 diesels.

It weighs 237 pounds less than an Allison automatic transmission, which Mack now offers in the Granite, said Roy Horton, director of product marketing. And the mDrive will be priced "thousands of dollars less" than a heavy-duty Allison, he added.

Like the on-highway mDrive, the HD version has 12 speeds forward with direct or overdrive top gears, and two reverse ratios, said Roy Horton, It has two power take-off mounts for running body and chassis equipment for varied applications.

Its clutch is automated so no clutch pedal is required. Operation of the transmission is controlled through a dash-mounted shift pad by selecting drive, neutral or reverse. For more demanding jobsite maneuvers, the premium shift pad can be operated manually to hold a gear, downshift or upshift.

The mDrive HD continuously monitors changes in grade (both up and down), vehicle speed, throttle position, acceleration, torque demand and gross vehicle weight. It automatically chooses the best gear for the road condition, allowing drivers to focus on the terrain rather than shifting gears, increasing safety on worksites.

The mDrive HD is based on the innovative design of the standard-duty mDrive, a proven performer that Mack made standard in the Mack Pinnacle model in October 2014. Any Mack dealer can service the product, Horton said, and it's supported by Mack’s Uptime services, which reduce downtime and maximize productivity through real-time monitoring and proactive repair scheduling.

Other features of the mDrive HD include:

• A transmission-mounted oil cooler to help maintain a correct operating temperature, despite repeated, heat-generating shifts common on a jobsite.

• Software packages specific to customer application, including Enhanced Construction for optimal on/off-road capability and full driver control over any terrain, and EZ Shift for smoother ratio changes shifts for sensitive payloads like livestock or bulk liquids.

• Rock Free, to free a truck from being stuck by rocking the truck back and forth simply by pumping the accelerator.

• Grade Gripper, which works with the anti-lock braking system to hold a truck from drifting backward on a downgrade without the driver touching the brake pedal.