Test Drive: ‘Mack is Back’

The Pinnacle, introduced in 2005, replaces Mack’s Vision and CH. Mack’s MP8 engine replaces the AC 427.

It was a great way to spend a clear June afternoon in Nevada: driving a bright yellow 2007 Pinnacle packing Mack’s new powerplant, the 13-liter Maxicruise MP8. With Joe Scarnecchia, Mack’s powertrain sales manager, along for the ride, I was bound for the hills surrounding Las Vegas to see whether the latest Mack would live up to its bulldog heritage.

Headed north on I-15, we immediately went into a two-mile climb of 2 percent or 3 percent. We reached 64 mph and 10th gear before the summit, and I assumed we had a 485-hp MP8, like the Pinnacle I’d driven on a seven-mile loop that morning. I was surprised when Scarnecchia said we had the 415-hp version.

“These are the right engines for fuel economy and power,” Mack’s David McKenna had said before the drive. The MP8 has the highest power density in the industry, at 32 to 37 horsepower per cubic liter, said McKenna, Mack’s powertrain sales and marketing chief.

After a few miles at 65 mph to get a feel for the truck and trailer, I went to the 75 mph posted speed limit, and soon we were storming I-15’s considerable hills north of Vegas.

All MP8s are configured to work well with 6-, 9-, 10-, 13- or 18-speed manual or automatic transmissions. During the 200-mile test, the MP8 let the Eaton 10-speed Ultrashift drop below ninth twice: once for a very steep climb, and once when we got trapped behind a triple-trailer rig laboring at 15 mph on a long hill. We lost some speed on the tougher grades. But only air brakes and Mack’s PowerLeash engine brake really slowed the Pinnacle down.

As we topped a hill and began to overtake traffic, I tapped the brake to disengage the cruise control and engage the PowerLeash. It quickly reduced the speed of our 70,000-pound rig. With the Pinnacle’s excellent insulation, we couldn’t hear the PowerLeash unless we listened for it.

“We’re confident it’s absolutely the quietest cab in the industry,” Jerry Warmkessel, Mack highway product marketing manager, said earlier.

He also said Mack is the first truck maker in the world to have as standard equipment the Bendix stability system, designed to prevent rollovers and jackknifing. That might have enabled the Pinnacle to handle better than I expected in an awkward, medium-hard curve.
Our momentum and the highway’s configuration seemed likely to bear us to far toward the shoulder and fling us too fast down the hill, but the Pinnacle straightened and then slowed.

As we drove, Scarnecchia explained some of the special features of the truck and engine. To increase cool airflow around the hotter-running ’07 engines, the Pinnacle has vents under the bumper, a wider frame and a narrower engine front. Additionally, the MP8’s camshaft drive gear train is located at the rear of the crankshaft, near the flywheel, thereby reducing engine vibration. Remove four bolts under the dash, and you can access the rear of the engine from inside the cab.

Pinnacle’s MP8 also comes in an Econodyne package, intended for mostly flat Interstate and less-than-truckload applications where fuel economy is a priority. Both the Econodyne and Maxicruise MP8s offer up to 485 hp and 1,660 lb.-ft. of torque.

McKenna says Mack expects about 4 percent better fuel economy with the MP8 than the engines it replaces. That would give the MP8 fuel economy of 6 mpg to 7 mpg, officials say.

If the Pinnacle lives up to Mack’s reputation for sturdy, long-lasting vehicles, then, as Warmkessel says, “Mack is back in the highway business, and it’s going to stay that way.”


THE PINNACLE SPECS

TRUCK: Mack Pinnacle Axle-Back 70-inch high-rise sleeper
ENGINE: 13-liter Mack Maxicruise MP8 with 415 hp @ 1,700 rpm and 1,560 lb.-ft. torque @ 1,100-1,200 rpm
TRANSMISSION: Eaton Fuller fully automatic 10-speed Ultrashift
REAR AXLE DIFFERENTIAL: 3:73
FRONT AXLE: Mack FXL 12,000 lb.
SUSPENSION: Mack MaxLite 40 EZ Air Ride
WHEELBASE: 239 inches
BBC: 112 inches
TRACTOR WEIGHT: 19,300 lbs.
TOTAL WEIGHT: 69,920 lbs.
FUEL MILEAGE: 7.9 miles per gallon

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