Lighter Granite MHD Aimed at ‘Munis’

Dec. 20, 2013

If this Mack looks like a typical municipal plow truck, that’s because it is. It’s the second version of the company’s Granite MHD (medium heavy duty), well named because it uses a midrange size, heavy-duty diesel: the Cummins ISL9. The MHD was introduced in 2011 with tandem rear axles, which are required for some duties but more than what many county, city and township road departments need. The single rear axle makes it more suitable for their usually lighter loads and winter snow plowing.

Test Specs

Truck: 2013 Mack GU432 Granite MHD
Engine: Cummins ISL9, 8.9 liters (544 cubic inches), 345 horsepower @ 2,200 rpm; 1,150 lb.-ft. @ 1,400 rpm, w/ Jacobs C Brake
Transmission: Allison 3000 RDS torque-converter automatic, 5-speed overdrive
Front axle: 18,000-pound Mack UniMax FXL18 on taper-leafs
Rear axle: 26,000-pound Meritor RS26185 on multi-leafs, w/ 5.38 ratio
Wheelbase: 180 inches
Brakes: Meritor Q-Plus S-cam, 16.5x6 front, 16.5x7 rear, with Bendix ABS and traction control
Tires & wheels: 315/80R22.5 Bridgestone M860 on the front, 12R22.5 Bridgestone M843 on the rear; on Accuride steel discs
Fuel tank: 66-gallon sleeved aluminum
Body: Henderson 10-foot stainless steel dump


Even with the tandem, the Baby 8 MHD with its smaller powertrain is a less costly alternative to full Class 8 Granites that come with large-bore Mack Power diesels and equally strong drivetrain components, said Stu Russoli, marketing product manager for construction. This was late last summer at Mack’s Customer Center, its former technical center in Allentown, Pa., where the truck was waiting for us behind the building. We both familiarized ourselves with the controls for the Henderson stainless steel dump body, because later we’d have to offload the sand that had been poured aboard to add some realistic weight. Then off we went for a tour of the area, during which we talked about this product.

A basic MHD is a Class 7 chassis rated right at 33,000 pounds gross vehicle weight, one pound under Class 8. Some commercial customers such as landscapers, machinery servicers, and others who need a lighter truck might choose it that way just to avoid the 12 percent federal excise tax applied to true heavies. But most will be built with higher-capacity axles, and this one definitely was, as indicated in the trucks specifications (see Test Specs sidebar).

Government agencies are exempt from the FET, so the Class 8 threshold doesn’t deter them from ordering what they need. Managers backed by enlightened elected officials can also afford to choose what holds up best. Here a Mack shines, as anybody who works for the Bulldog brand will tell you, including Russoli. “It’s a premium truck and it will command a premium price,” he said.

The 8.9-liter ISL9 is a major cost reducer, saving several thousand dollars over a bigger MP7 or 8 diesel. The Allison 3000 RDS automatic transmission lists at $12,000 to $15,000 over a manual, but would cost thousands more if it were a 4000 series needed to handle the output of a bigger engine. Allisons are virtually standard in municipal fleets because they save more in wear and tear on drivelines and people than they cost.

Another money saver is interior trim; this truck had the base-level Thoroughbred package so its seats and the door and wall panels were covered in vinyl. But it neither looked nor felt cheap. And certainly premium were the basic items from the heavier Granite line: a stout Cornerstone chassis that Rusolli said was stiffer than many competitors’; a rugged galvanized-steel cab with stout doors; a large, two-panel dashboard that’s set up with nicely designed gauges, switches and controls, including big rotary knobs for the HVAC that are easy to see and quick to use; and a composite hood that housed the engine and its accessories, and tilted easily for servicing and repairs.

On the test drive, the MHD felt rugged and rode like it. There’s only so much that beefy leaf springs can do to soften blows caused by bowed and broken concrete and undulating asphalt, so the truck bounced over them. On smoother surfaces it rode decently, and with a heavy plow hitched to the mount up front it’d probably settle down. Likewise for a heavier load; there were about 5 tons of sand in the stainless steel body, far less than what the truck could haul.

The powertrain was a smoothie, though. The 8.9-liter Cummins was lively and readily revved to 1,900 and beyond when I put my foot into the pedal, and the Allison automatic shifted positively but without any harshness. This one was a 5-speed, so it had just one overdrive gear and that, along with the 5.38 rear axle ratio, caused the engine to spin busily at highway speeds, though well within the engine’s bounds. Still, if I were the fleet manager, I’d try to sell the folks on the city council or township board on a 6-speed to lower revs and save some fuel.

Like all other Macks, the MHD was assembled at nearby McCungie, so is a product of the Leheigh Valley. So is Russoli, who said he spent the first 39 years of his 43-year life here. With other Mack executives, he’s now based in Greensboro, N.C., and he likes it, especially for its more moderate climate. But he enjoys returning for visits like this one and remembers enough about Allentown, Bethlehem and other communities to ably guide me around the area during our drive.

“Do you want to go past Mario Andretti’s house?” he asked at one point. I’m not a big fan of motorsports, but I recall Andretti always being identified with Nazareth, Pa., so, sure! Rossoli had me make a right turn onto Rose Inn Boulevard, a wide residential street that turns into a country lane. After a couple of miles, off to the left and hiding behind some trees, was the house. “We could see it if we were going the other way, coming down the hill,” Rossoli assured me as we began a mild ascent. Closer to the road and in plain view, though, was the former home of Mario’s son, Michael Andretti; it’s turreted like a castle but has big glass windows. Michael sold the big house before moving to Indianapolis, Russoli said.

“Over there’s Martin Guitars,” he added as we rolled by a modest-size factory nestled among the homes and green hills in this region. If you’re a musician or watch Antiques Roadshow on PBS, you know that C.F. Martin & Sons, a sixth-generation family business, has been making guitars in America for a long time. Wikepedia says its founder, German immigrant Christian Frederick Martin Sr., moved to Nazareth from New York City in 1838. That’s 67 years before the Mack brothers moved from NYC to Allentown.

I can’t play a guitar but I can drive a truck, and the Granite MHD with the Allison was more like wheeling a big pickup around town. The truck was short and looked official enough that I didn’t worry about going through residential areas, though I saw no restriction signs on the streets we traveled. With the short 180-inch wheelbase and power steering it turned easily, and with big windows and good mirrors it was easy to maneuver and back up. 

By the way, this is a show truck, which explains some of its bright-metal trim. Why white paint, though? Shouldn’t a muni truck be Omaha Orange or maybe yellow or red, especially if it’s going to plow white snow? Rusolli agreed, but noted that it could easily be repainted after it’s done making the rounds at trade shows. Whichever municipality ends up owning it might do that, but if not, it will still have a rugged and capable piece of equipment.