Through the mountains in a Mack
Mack’s new mDrive AMT takes the treachery out of long mountain drive
By Jack Roberts
“Mack is in a good place these days,” says Kevin Flaherty, senior vice president for Mack in the United States and Canada. “Our new engines are a homerun. The introduction of our ClearTech SCR technology proved to be a total non-event.” Plus, says Flaherty, Mack saw a 12-percent increase in fuel economy in its 2010 Mack engines (on trucks equipped with new Mack aerodynamic equipment) compared to 2007 Mack diesel engines.
The Secret Formula
Automated manual (AMT) and automatic transmissions are making tremendous inroads into the heavy-duty commercial vehicle market. In fact, Flaherty believes that in just a few short years, a full 40-percent of new Mack trucks will be leaving the plant spec’d with mDrive AMTs. Automatic transmissions aren’t new, of course. But early models faced reliability issues in rugged applications. Manufacturers have steadily improved their designs to insure dependable service on heavy-duty vehicles. But the real breakthrough for automatics has been the increasing sophistication of on-board electronic control modules. These mini-computers allow vehicle components to “talk” to each other electronically and tailor their performance to match the driver’s needs in ever-changing driving situations.
In the case of the Mack mDrive, McKenna explained to me, the transmission starts out by sensing the load behind the tractor. In our case, we were pulling a flatbed loaded with granite blocks, totaling 79,000 pounds and change. The mDrive also has an inclinometer. Which means it can sense any grade the truck is on. Using this information, the transmission can talk to the engine and the engine brake, which tells it how much available horsepower and torque is available to either get the load moving or slow it down.
Because of this, the mDrive can make thousands of split-second calculations to determine the correct gear and the correct shifting sequence – including highly logical gear shifts – to give drivers the optimum amount of power they need at any given moment. “The key to the mDrive – and the secret to why it works so well with Mack MP engines – is that data stream,” McKenna notes “When we install a supplier-built transmission in one of our trucks, we only provide that transmission with about 80 percent of the data generated by the engine and engine brake. The mDrive has access to 100 percent of our powertrain telemetry. And that makes all the difference in the world: This transmission is fully integrated into the overall powertrain, giving you superior performance.”
A 30-percent workload reduction
A transmission can analyze all the data in the world. But it cannot replace a human when it comes to dealing with traffic and changing road conditions. That’s why Mack and Volvo engineers made certain to design the mDrive with intuitive, easy-to-access manual controls.
I found this out early in our drive as I started up a long freeway ramp. Reaching over, I hit a button at the top of the mDrive labeled “Perform.” By doing so, I was telling the transmission and engine that I needed extra horsepower to get the rig rolling. As a result, the mDrive switched to a more aggressive gear selection and shift sequence, while the MP8 diesel churned out additional horsepower. Once we hit cruising speed, the mDrive automatically disengaged Performance mode and we settled in for a long drive west.
It was in the mountains – or, more precisely, coming down the mountains – where I gained a full appreciation of the mDrive’s capabilities. After letting me fan the brakes down a few long grades as a warm-up, McKenna suggested letting the transmission hold us as we went down the next one. So, this time, as we crested yet another mountaintop, I reached over and manually downshifted from 12th to 11th gear. The engine brake engaged immediately, and working with the transmission, held the Pinnacle at my desired speed down the slope.
At first my right foot hovered nervously over the brake pedal waiting to pounce on it if our speed started get away from me. I needn’t have worried: this transmission is more than capable of holding its own down a long, steep mountain grade. On a few steep grades, an additional downshift to 10th gear might be in order. But, again, this was easy enough to do to. And right away, I felt the engine and the transmission working together to give me more aggressive retardation to keep the vehicle speed right where I wanted it. There was no question the mDrive was giving me a definite safety advantage on those steep down grades. And the Pinnacle’s brakes were getting a decided break in terms of over-use, over-heating and maintenance as well.
I found the mDrive to be just as effective when it came to climbing grades. It downshifted as needed to lug us uphill efficiently with no casting about for the right gear to get the job done. And once we were on the Eastern edge of the Smokies, I found the mDrive also works with the Pinnacle’s cruise control, engine and engine brake to maintain desired vehicle speed without engine over-revs or sudden spikes in fuel use.
Afterwards, I calculated the transmission probably cut my workload by as much as 30 percent considering all the gear shifts and brake applications I did not have to make while driving the truck.
