Can a box full of gears have a personality? Mack’s mDrive and Volvo’s iShift are one and the same automated transmission. Like the engines produced by the two sister companies, there is little if any difference in the hardware. The programming gives each its performance profile.

In the early days of automated manual transmissions (AMT), it was neat enough that they shifted gears all by themselves. The early versions weren’t imbued with a great deal of imagination; they shifted when programmed to, and so were pretty rigid in the way they performed. Getting the engine and the transmission talking has been the challenge.

The Mack/Volvo people have an edge here. They build and program their own engines and their own transmissions, so there’s a very high degree of communication and understanding between the
two.

Since there are distinct differences between the Mack and Volvo engine power maps, there should be differences in how an iShift performs versus an mDrive. I’ve driven both; both work extraordinarily well for the intended application, and neither represents any kind of programming or performance compromise.

Mack’s software engineers have invested thousands of hours writing code to give their transmission a Mack personality — if you will. Just as Volvo’s people have done for iShift. You might think there are savings to be had by doing this job just once, but this gets to the heart of brand differentiation.

mDrive shifts just the way a Mack driver would shift to get the expected performance from the Mack MP7 or MP8 engine.

The MPs are programmed to produce power and torque based on three performance profiles: Econodyne, Maxidyne and Maxicruise. mDrives are programmed to compliment those performance profiles, and they offer three driving modes on top of that for additional flexibility.

Economy is the standard mode, which tilts obviously towards fuel savings over performance. The optional Performance mode gives the driver 150 – 200 rpm extra in a given gear for a little more get up and go, or for heavier loads. Easy Shift is an optional mode with a less aggressive shifting schedule. This would work well in livestock or liquid tank applications.

The outfit I used for this test had a 505-hp MP8E (Econodyne) engine with the optional Premium mDrive package, offering the full range of driving modes and performance options. The Fleet spec (standard) is limited in functionality, but many of the features found in the Premium version can be added individually as options to suit fleet tastes. We had a 60,000 GVW, five-axle combo for the test.

FIRST, THE TRACK

Before we left the Customer Center, Scott Barraclough, Mack’s powertrain sales manager, took me onto Mack’s engineering test track that has a 15-percent grade obstacle and some open pavement where you can play a bit without worrying about traffic.

I like to try baffling an AMT by getting on and off the throttle and brake pedals at varying speeds to see if it goes hunting and pecking for a gear. Get it up to 20 mph or so, hit the brake, knock it down to 10 mph, hit the throttle, get it up to 30 or so, hit the brake, etc. mDrive stayed right with me through this exercise, up- and down-shifting, revving and retarding the engine as necessary. And upon coming out of a series of start-stop maneuvers, with gentle throttle application, it skip-shifted its way up from 4th, to 6th, to 9th etc. If it didn’t need the gear, it went right past it.

The optional GradeGripper feature works as advertised, holding the truck for up to three seconds on a hill, and modulating the brake release as throttle is applied. This is sheer brilliance, and should be required on all trucks with AMTs (it requires a certain ABS system as well).

THE OPEN ROAD

Scott and I took the truck on a 150-mile trip over a variety of terrain and driving conditions to get a better sense of how the transmission deals with ascents, descents, urban driving cycles, and of course, highway driving.

Each taxes the programming in a different way, and I wanted to see if the engineers had given it the brains to handle everything North America could throw at it.
 

The mDRIVE shifter is easier to operate
than the radio it shares dash space with.

Leaving the new Customer Center in Allentown, we headed northwest on Rte. 309 intending to hook up with I-81, then
I-80, and finally the I-476 for the return leg of the trip.

Rte. 309 is one of those eastern-Pennsylvania two-lane classics where people’s front porches sit mere feet from the roadside. A cart path some 250 years ago, today it’s paved, and has traffic lights.

On a high-driver-workload road like this, an AMT really earns its keep. Not that a good driver can’t manage changing traffic conditions, challenging driving conditions and a stick-shift too, but mDRIVE optimizes the process. It nails every gear change for best performance or fuel economy, while the driver’s head spins back and forth watching for curbs, utility poles, cars, and baby carriages on the edge of the sidewalk.

Nor far from Allentown, Rte. 309 passes over Blue Mountain. It’s four or five miles up and the same distance down over varying grades. We had time to compare performance and economy modes while climbing. We started into the hill in economy mode, and mDRIVE dropped a few gears to keep us climbing, but at lower rpm where the torque is — and the fuel savings.

As the grade changed, the transmission read the engine speed, sensed the grade, and in some cases dropped or gave up a gear. It sometimes let the engine lug a little. That’s how it’s supposed to work. Optimizing engine output for the conditions.

In performance mode, it basically ran a gear down from economy mode. That gave us a few hundred rpm more, and correspondingly more horsepower. It pulled “better” but we gave up some fuel economy. The shift points were higher too. Rather than lug down to 1,100 or 1,200 rpm (peak torque and peak fuel economy), it would downshift between 1,300 or 1,400 rpm.

Coming down the other side was interesting. On a six-percent downgrade on a narrow two-lane road, you don’t want the truck getting away from you.

The cruise control was off as we came over the top, so I backed off the throttle near the top, and let the engine revs drift down to 1,000 rpm or so, with very little throttle input. It didn’t take long to get up to speed again, though, and there we were in tenth gear at 1,400 rpm at 45 mph heading downhill.

From a retarding point of view, that’s not optimum. I punched the “minus” (-) button on the shifter console, downshifted, and bumped the rpm up to 1,800. With plenty of air going into the engine, the retarder performance improved, and we easily held speed on the grade. The PowerLeash pulled us down a few mph to where the engine was running about 1,600 rpm, with enough retarding power to hold our speed steady.

That was fine for that stretch of the hill. So just for the heck of it, I hit the downshift button again.

You’d need to be a very confident driver to downshift in that situation — revving to 2,100 rpm and hitting the gear exactly right. You’d only get one chance. Miss it and all of a sudden you’re going 10 mph faster than you should be and … mDRIVE nailed it, as it’s supposed to, with no hesitation about topping out the rpm before getting back in gear. I’ve seen other AMTs decline a shift like that one.

The only problem with the set-up is the minus sign button is a rather small target, and you need to divert your eyes from the road to get it right. If you hit the “plus” (+) button instead and upshifted, you’d be in a difficult position. Of course, there’s always the brake pedal.

On flatter but busier terrain through the town of Tamaqua, mDRIVE shifted happily away as we lurched from light to light winding our way through the narrow streets. It’s nice to know your transmission is working to save fuel while you’re working to save pedestrians and utility poles.  

Mack’s mDRIVE
and its older cousin, Volvo’s
iSHIFT (above) both have an edge over older automatics.

Out on I-81, we had the chance to test the Cruise ‘n’ Brake feature and its ability to predict shift points in an ascent. Interstate 81 has a lot of rolling hills that require some discipline from the driver. The grades are shallow enough that usually a single downshift is all that’s needed to get to the next crest. It’s tempting to drop a second gear if you want to motor on up the hill, but of course that hurts fuel economy. With a manual box, that bit of discipline is all that stands between you and a higher fuel bill.

In economy mode, the transmission will avoid downshifting until the engine is close to the lower end of the peak torque band. In performance mode, it’ll make that downshift about 300 rpm sooner.

There’s a grade sensor built into the transmission, so it can detect changes in the grade. If the hill was beginning to level out, it might decide to preempt the downshift until it sensed either an increased demand for power or a steepening of the grade.

Depending on your appetite for excitement, if you leave it in cruise control, the engine/transmission combo will decide when to shift. Off-cruise, the driver can simply back off the throttle a little and the transmission will delay the downshift, sensing an easing in the demand for power.

The driver can influence the downshift point by pressing the M (manual) button on the shift console, too. That will hold a gear until the engine gets way outside the normal shift parameters. The driver has the benefit of seeing what’s ahead, and if 100 rpm would be enough to make the crest without a downshift, all the better. The engine can do it.

What I really like about this transmission is its logic. It won’t shift simply because some engineer programmed it to do so at a certain rpm.

So, on I-81’s rolling grades, we dipped below the normal shift point several times, saving a little fuel in the process. The transmission never signaled its objection until we were well below the optimum shift point by 150 rpm or more (in manual mode).

On a downgrade, the driver can set the optional Cruise ‘n’ Brake to a top roll-out speed, and the mDRIVE and PowerLeash engine brake combination will do its best to maintain that speed, including initiating a downshift or a series of downshifts to optimize engine revs up to maximize the retarding power. It rolls the engine brake on in stages to increase the power as needed, so it’ll engage the first stage, then the second, and finally the third.

Interestingly, the driver doesn’t have a choice of stages. The PowerLeash is either in auto, as just described, or in the oddly named “Latch” mode, where it’s full on and the transmission can downshift to gain more retarding power.

On a roadway like I-81, with the Cruise ‘n’ Brake speed set at 70 mph and running speed set at 60 mph, the PowerLeash did its job, unobtrusively keeping the truck between those preset speeds. Nice feature. Mack says it will be officially changing the name from Latch Mode to MaxBrake next year.

The rest of the ride back to Allentown wasn’t much of a test for the transmission. Basically flat interstate — once in top gear, it stayed there. Ho-hum.

I did check out the MackCellerator feature, though. It’s a kick-down switch in the throttle pedal that initiates a downshift and gets the truck up and running with some urgency. Useful in a passing situation.

There’s a detent in the pedal, and once pushed past that, the shift happens. It’s optional on the Fleet spec, and standard on the Premium package. The alternative is to press the “plus” button.

As I’ve said in the past, this 12-speed AMT from the Volvo Group is a winner — regardless of the badge it wears. Mack has given it Mack performance attributes, as Volvo has done with its version.

It’s not a one-size-fits-all gearbox, but some highly competent technology tailored specifically for certain applications. The difference is in the programming, not the color of the box.