Mack MHD Is A Trimmer 10-Wheeler

Nov. 8, 2011

Any modern truck is tailored to its intended job, and so it is with this Mack Granite MHD. It’s a lighter heavy truck that uses an 8.9-liter Cummins ISL9, which weighs several hundred pounds less, and is priced several thousand dollars under the tab for a regular Granite with a large-bore Mack Power diesel.

Any modern truck is tailored to its intended job, and so it is with this Mack Granite MHD. It’s a lighter heavy truck that uses an 8.9-liter Cummins ISL9, which weighs several hundred pounds less, and is priced several thousand dollars under the tab for a regular Granite with a large-bore Mack Power diesel.

Announced earlier this year and recently put into production, it’s aimed primarily at municipal fleets and private operators who don’t need a full-fledged Class 8 truck but still have some heavy chores to do. The MHD comes as a 10-wheeler, with tandem rears but no lift axles, and only as a straight truck. A single-rear-axle version might expand its appeal to munis, but Mack has no plans now to take it in that direction. For one thing, an otherwise premium Granite might be too pricey against medium-duty trucks that compete for such business.

Aside from the smaller engine and accompanying transmission, the MHD is a true Granite, with a solid steel cab, hefty frame rails, and everything else found on heavier versions. It felt and drove like a Class 8 truck but with somewhat less oomph, even though its Allison automatic transmission compensated by sending constant power through the driveline. The Allison also made it a very easy truck to drive, and is typical of how city and county fleets buy their trucks.

I met this new, blue MHD at the Mack Customer Center, housed in the former technical center complex in Allentown, Pa., and not far from Macungie, where the truck was assembled. A few years ago Mack moved its headquarters to Greensboro, N.C., but fleet managers who want to see and inspect their new trucks still travel to A-town and this center, which also houses the independently run Mack Museum. If you go there, plan to spend some time with this company’s proud past.

John Walsh, Mack’s press relations manager, picked me up at the airport and drove me to the center for a meeting with Curtis Dorwart, the builder’s vocational segment manager. He explained the MHD’s features and accompanied me as we drove the MHD to a quarry outside of Easton. Here I met Bob Evans, a retired Mack engineer who now works as a photographer. He guided me along the trails that meander through the complex, and we both watched out for working trucks that were constantly coming and going.

Decent ride

Otherwise Dorwart and I stayed on area streets and highways, some smooth and some rough, as one would expect in a cold climate. But it was sunny and balmy on this mid-August day, enough to run the powerful air conditioner at first, then shut it off and roll down the windows to enjoy the comfortable outside air. We rolled ’em back up while at highway speeds, and the cab’s interior then was very quiet.

Folks at the A.B.E. Materials quarry had put 11.69 tons of #10 stone in the dump bed to give the truck a realistic working weight and move gross vehicle weight to 58,400 pounds, according to the scale ticket Dorwart handed me. Technically this was 3,800 pounds over its rated GVW, based on axle capacities. The load settled down the AL461 rear air suspension, and my suspension seat took care of any harshness that got into the cab. Dorwart’s passenger seat was on solid mounts, but he didn’t bounce around much.

The ISL9 diesel and its natural gas-fueled brother, the ISL-G, are the only Cummins engines now used by Mack. It dropped the Cummins ISX a while ago when it quit making the CL long conventional, and for a time used only Mack engines, something it’s done off and on for much of its long life. Mack uses the ISL-G in its TerraPro MR heavy low-cabover that works primarily in the trash business.

The MHD could conceivably have used a midrange diesel from Volvo of Sweden, its corporate parent, but that would’ve required expensive certification of a new engine with the U.S. EPA. Cummins’ ISL9 is an increasingly popular product in the U.S., and other truck builders also employ it in various models similar in mission to the Granite MHD.

Limited performance

Smaller displacement of course limits horsepower and torque. This engine’s rating was 345 horsepower and 1,150 lb.-ft., which was fine on level streets because all I had to do was stomp on the accelerator and the 6-speed Allison with its locking and unlocking torque converter made the most of whatever was at the flywheel. With our moderate load, there was no problem keeping up with traffic. Only on a narrow, winding highway on the outskirts of Easton did we slow up motorists, as the truck’s bulk and slightly top-heavy feel kept me cautious.

On steep grades the ISL pulled gamely, though our road speed dropped to as low as 45 mph on one long hill. If the engine had been bolted to a manual tranny of some kind (an Eaton 10-speed is standard), my right arm would’ve been rowing through the gears.

Mack prices the 3000 RDS auto tranny in this truck at $15,000 over the manual, Dorwart said. That’ll buy a lot of clutches and U-joints, and there are still a lot of guys out there who can handle a manual, so the privately funded fleet will usually stay with a crashbox. Municipal fleets, though, do more than haul gravel, and the Allison is true salvation after long hours of plowing snow and no letup in sight.

Otherwise this Granite looks and is equipped like any other Granite, and that’s a good thing, because it’s roomy, comfortable and rugged. It replaced Mack’s venerable RD and other vocational trucks which were rugged but definitely not cushy. Sometimes I wonder how guys withstood driving the older models.

Then I remember an outing in Boston about 10 years ago, while the notoriously expensive Big Dig was still a-diggin’, when I drove a CL and an RD. And I came away preferring the RD because it was more compact and easier to see out of. Mack had improved the RD over the years, but the Granite is far, far better.

This Granite MHD has a different powertrain for a slightly different mission, but it’s still got Mack’s durability and modern-day comfort. It could work for you, but otherwise there are Granites with heavier duty capabilities and bigger MP diesels just waiting in any Mack sales guy’s data book to get to work now, or when prosperity returns.