Test Drive

Photos and Story by Steve Sturgess | June 01, 2012

Smooth and Smart

With further aero refinements and an intuitive transmission, the Pinnacle proves its lofty name is well deserved.

Automatic transmissions are making inroads in the North American truck market. Volvo is delivering 40 percent of North American trucks units with its I-Shift automated 12-speed in the driveline. Partner company Mack has done them one better in the Pinnacle, with more than 40 percent of produced units featuring Mack’s mDrive, an automated 12-speed that is smart and slick.

Driving this Pinnacle across the Appalachians was a breeze with mDrive’s selection of gears according to road grades.

That’s particularly evident after my 700-mile March haul in the driver’s seat of a Pinnacle, grossing nearly 80,000 pounds with a loaded flatbed. From the Mid-America Trucking Show in Louisville, Ky., we crossed rugged West Virginia mountains to get to Mack’s Customer Center in Allentown, Pa. I shared the driving with David McKenna, a 32-year Mack veteran.

The Pinnacle is not new. In fact, it goes back to the launch of the Vision in 1999, and in its basic cab structure back to the launch of the Mack CH in 1988. But the Vision was a complete redo of the earlier truck with more room for the driver, a total aero package and the “M” shape added to the grille. The Pinnacle’s 2006 introduction coincided with the launch of the MP engines for the 2007 and later emissions systems.

At the 2011 MATS, Mack Product Marketing Manager Jerry Warmkessel said the Pinnacle had been through the National Research Council wind tunnel in Ottawa, Ontario, where it delivered a 6 percent gain in fuel economy over previous highway models. Further, Warmkessel said the combination of aero improvements and intelligent mDrive transmission with the new selective catalytic reduction (Mack calls it ClearTech) emissions reducing technology could offer fuel savings greater than 12 percent.

A low-rpm cruise package called the Super Econodyne debuted at this year’s MATS. Gearing so the truck cruises at 65 mph and 1,160 rpm means another potential 2 percent gain in fuel economy for the right applications.

The Pinnacle I drove featured the MP8 at its highest rating: 505 hp with 1,760 lb.-ft. torque. It’s the 13-liter version of the overhead camshaft engines developed to meet 2010 emissions regulations. Though the MP8 is basically the same engine as the Volvo 13-liter, the Mack has its own personality – in this case, the Econodyne profile, which has long been part of the Mack brand. A feature of this profile is EconoBoost, an on-demand torque boost when the full throttle is held for three seconds. The engine adds as much as 200 lb.-ft. at any speed from 1,300 rpm.

It takes an intelligent transmission to account for that. The mDrive has common mechanicals with the automated Volvo I-Shift, but it’s by no means the same transmission. It has unique programming to match it to Mack engines and their distinct power and torque curves.

Threading my way out of the Kentucky Fairgrounds, I was impressed by the way it picked up gears, yet idled easily in traffic. The seating provides an excellent view over the sloping hood, and well-placed mirrors allow comprehensive visibility.

The mDrive doesn’t just respond to the engine – it drives it. Gears are selected according to road conditions. The transmission has an inclinometer so that it knows if the truck is going up- or downhill. It knows what the driver wants through the throttle position and tells the engine what is needed. Starting out, it gradually closes the clutch for an impeccable response to the first squeeze of the throttle pedal. When it’s time to shift gears, the transmission commands the engine to back off and break the torque flow. The transmission then float-shifts to the next gear, exactly matching engine revs to smoothly swap gears.

In an upshift, the transmission may call on the engine brake to slow the rpms, snapping shifts faster than even the best driver could. At Mack’s Customer Care Center test track, when I accelerated up a 10 percent test hill from a standstill, the Mack just picked up gears as it accelerated away, block shifting one to three, then four and five to make the most of the transmission’s capabilities.

Such an extreme start was never necessary on the highway, but the transmission would often skip gears, either to make the most of the acceleration or to bring in the Powerleash engine brake for maximum retarding. At the same time, it worked toward optimum fuel economy. Negotiating Kentucky hills at start, the numbers on the dash display climbed to a very creditable 7.3 mpg. Then as we got into the serious climbs of West Virginia into Allentown, fuel economy crept back to 6.9 mpg — not at all bad given the heavy load and the mountains.

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