Equipment

Test Drive: Mack's mDrive Programmed for Bulldog Shifting

November 2010, TruckingInfo.com - Test Drives

by Tom Berg, Senior Editor, Senior Editor - Also by this author

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Knowing that Mack and Volvo are sister companies, it would be easy to dismiss Mack's new mDrive as an I-Shift with a dog's name.


Like Volvo's automated mechanical gearbox, Mack's mDrive has 12 forward gears that change smoothly and appropriately. It's got an automated clutch so all the driver has to do is steer, step on the accelerator or brake, and enjoy several assist features as he stops, starts and motors down the road.

But mDrive is not a relabeled I-Shift, insisted Dave McKenna, Mack's director of powertrain sales and service, during a visit to Greensboro, N.C., where the two companies' headquarters are next-door neighbors. Yes, mDrive's basic mechanics come from Sweden, but its electronic controls have been carefully programmed to work with the horsepower and torque curves unique to Mack's MP7 and MP8 diesels.

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Furthermore, MP (for Mack Power) engines are not just repainted Volvo diesels, even if both product lines are made in the same plant in Hagerstown, Md., McKenna explained. MPs are programmed to produce power and torque with characteristics peculiar to three tuning types: Econodyne, Maxidyne and Maxicruise.

"It took programmers writing code for hundreds of hours to make the transmission work with the engines' controls," McKenna said so earnestly that I didn't have the heart to call the mDrive a reprogrammed you-know-what. If it is, it's been reprogrammed four times, because that's the number of shift modes customers can choose from, and that's a lot of computer code available only from Mack.

On the road

Some of this was imparted to me while under way in a candy-apple-red Pinnacle Axle-Back tractor McKenna lined up for this test drive. Dave Troupe, an engineering technician, had parked it at the headquarters, all ready to go with a 48-foot van ballasted so the rig weighed close to the 80,000-pound limit, including the three of us in the cab. They directed me out the lot and onto a frontage road that parallels Interstate 40 (which, as almost every trucker in the Southeast knows, runs right past Mack's and Volvo's houses.)

Right out of the lot I sensed that the mDrive in this tractor had a leisurely way of doing things. That's because it had the Economy mode,which upshifted at low rpm - usually 1,400 in most gears - just like drivers are supposed to do, especially in lower gears. This is akin to "progressive shifting," where you upshift at very low rpm in lower gears because you don't need much power there. Then you rev the engine progressively higher as you move upward in gears and road speed, where you need more horses.

The mDrive also skip-shifted a lot, going from 1st to 3rd to 5th and so on. More often it started out in 3rd or 4th and skipped one or more gears each time if the pavement was level and my foot was light on the pedal. The automated clutch engaged more smoothly than I could've done it, which made the higher-gear starts possible. A readout on the dash told me what gear it was in, otherwise I probably wouldn't have known - the tranny is that smooth.

As we headed west on I-40, then swung north on U.S. 52 toward Fancy Gap and Mount Airy, I noticed that the tranny didn't downshift much. "It's programmed to downshift below 1,100 rpm, which is where the torque peak is," McKenna explained. "This can save a significant amount of fuel" over more performance-oriented shift schedules that use higher, more thirsty revs.

At first I more or less went with the program. The 13-liter Econodyne engine just plugged away on a 4 or 5-percent upgrade, and we'd top a hill at maybe 40 mph. The engine was so quiet that I wondered if it really was working, but not many other big rigs were passing us, and when they did they weren't by any means blowing our doors off.

"Yeah, but you need rpms for performance," I said smugly, and promptly punched the "Perf" button on the tranny selector. This caused a downshift and about 300 more revs, and then the rig would top a hill at 45 or so. Perf would hold for about a minute, then its indicator light would switch off and the controls would revert to Economy. In production models, however, it will stay in Perf until the ignition is switched off or the driver turns off Perf by punching it a second time.

The transmission also can be downshifted without taking your hands off the wheel by pushing the accelerator pedal toward the floor until a detent is felt. Then, if a lower gear won't overspeed the engine, the tranny will go down a step and revs will climb, sort of like "passing gear" in an old Ford-O-Matic or Chevy Powerglide. This is called MackCelerator, a clever name that McKenna coined. But stomping on the pedal strikes me as extreme, so I preferred the Perf button.

For guys who consistently want to make some time, there's the Performance mode, also for Econodyne engines, which has shift points about 200 rpm higher and might be better for rolling terrain, McKenna said. What it does is duplicated by the Economy mode's Perf button, but of course you don't have to punch the button. Like the Economy mode, Performance mode can be matched with an Econodyne engine. There's also a Performance mode for Maxicruise engines, which raises shift points 150 rpm over Economy.

The fourth mode is Easy Shift, also called Comfort Shift, which shifts slowly and smoothly, and emphasizes skip-shifting. It can be had with Econodyne or Maxicruise engines. Comfort Shift was first developed by Volvo in Europe for motor coaches, so passengers aren't pushed fore and aft "like bobble heads," McKenna explained.

"It's almost like a CVT," a continuously variable transmission, in how it behaves, he said. In a Mack, Comfort Shift will be good for haulers of cargoes like livestock (which also don't like being pushed around), and bulk liquids in smooth-bore tanks, which can surge up and back and make life too interesting for a driver.

Initially, mDrive won't be available for Maxidyne engines in vocational trucks, McKenna said. That'll come later, when enough on-road mDrives are in service to be sure they're working as designed. Mack's allotment of mDrives is sold out for the rest of 2010, even though there's not been much marketing of this product. Mack also offers Allison's full automatics, and Eaton's UltraShift - but not the smoother working UltraShift Plus, which is closer to direct competition for mDrive.

A feature on our test tranny was Econo Roll, which made it freewheel under certain no-power situations. This startled me the first couple of times it occurred. Suddenly the engine dropped to idle and it felt like we were out of gear and possibly out of control, even though we weren't. Technically the tranny's rear box was disengaged but its main box was still in gear, so it's legal. A touch on the accelerator or brake pedal immediately re-engaged it and revs rose again. It can save some fuel, but I'm not the only one who thinks it's disconcerting, so Econo Roll won't be on production models.

One feature that is being included is Grade Gripper, which works with the anti-lock braking system to apply the service brakes while the rig is sitting on a hill. Stepping on the accelerator releases the brakes and the rig moves out. It's a definite convenience, and one that'd be even more useful on trucks or tractors with manual transmissions.

The Truck

This quiet and comfortable Pinnacle tractor's diesel was 2010-legal, with the selective catalytic reduction system Mack calls Clear Tech, signifying the color of its exhaust. Aftertreatment equipment is stacked on the right side of the frame, under the cab. Like other 2010-spec diesels (and '07s, for that matter), there's no odor, either.

The tractor also had Bendix-made Adaptive Cruise Control, which alters road speed to match that of traffic just ahead. It'll beep warnings if its radar-fed brain thinks you're getting too close to the next vehicle, and apply the service brakes if you don't slow down

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