Near a half century ago, back in the bad old days, big trucks had at least 10 forward gears. We weren’t just showing off our gear grindin’ skills, the common Cummins and Detroit engines of the 60s had such narrow powerbands that they could barely handle a 400 RPM drop from maximum governed speed before a downshift was required. Thus every stop sign and red light required going trough most of those 10 gears all over again… That got old fast!
The basic architecture of Mack’s diesel gave them a displacement disadvantage vs. Cummins, which they largely resolved by early adoption of turbocharging. That brought a bunch of other benefits like lower emmissions and better fuel economy as well as consistent performance regardlesss of altitude. Then misters May and Pellizoni, Mack engineers, saw another benefit… They could tune an engine’s power curve by careful matching of turbocharger and fuel pump settings. Thus from their test cells sprang the mighty Maxidyne, with peak torque moved clear down to 1200 RPM while the power peak was moved down to around 1800 RPM while the governor still shut down the party at 2100. The result was an engine that only needed a simple 5 speed transmission and with a 900 RPM wide powerband from 1200 to 2100 RPM, and could run from 36 to 63 MPH without needed a single stirring of the gearshift lever. And while that transmission may have seemed short on gears, it had no less than triple countershafts… The scrapyards are full of ’em, because they were so indestructable that hardly anybody ever broke one!
With this massive competitive advantage Mack was the go-to truck from the mid 60s through the eighties, filling fleet rosters everwhere. Then in the 80s fleet managers began to suspect that winding the Maxidyne up to 2100 was eatin’ up the fuel too fast. Mack responded with a Maxidyne governed at 1800 cutting the power band back to only 600 RPM, and pretty much created the prototype for all of today’s big truck diesels. Then Mack developed a low speed Maxidyne, with a power band from 1000 to 1800 RPM so drivers could still enjoy a 5 speed transmission.
Come the 90s and speed limits rose and truckers demanded more power, but with the exception of the rare 400 HP Maxidyne V8, the Maxidyne offerings topped out at only 300 HP. Thus Mack’s conventional 350 and 400 HP engines took over the highway market. But the Maxidyne had an even more loyal group of fans, truckers in the construction biz who appreciated the Maxidyne’s ability to pull up hills and through muck all the way through it’s broad power range when a gearshift would only bog you down worse… So while the Maxidyne may have been exiled from the highways, it lived on in construction trucks everywhere.
Comes the 21st century and Volvo buys Renault and Mack in a package deal and sets out to plant a bulldog on the hood of their Volvo trucks and pass it off as a Mack. While the six cylinder Maxidyne finally got a bump to 370 HP in 2004, by 2007 Mack engines had given way to Volvos in red paint with a few software tweaks. Then Volvo’s automated manual transmission was offered and the durable Maxitorque all but forgotten. But some Maxidyne high torque ratings were carried over to the new Volvo engines, and wide ratio 6 to 10 speed transmissions were still technicly available.
Couple months back I saw a near buried blurb from Mack noting that Maxitorque transmissions were still available, but didn’t seem to be as many models as before. Confirmed from an authoritive sounding source that the wide ratio transmissions are no longer available, took a look around dealer’s inventory and couldn’t find them in any new trucks in stock. Having made little mention of the simple Maxidyne option, Vovo has succeeded in making us forget about it in preference to their complex proprietary automated manual transmissions.
‘Cept some of us won’t forget the joy of driving a truck that shifted gears as easily as a car, only downshifting for the real hills instead of once or thrice for every little rise. Maxidynes, long may rule the roads!
GearheadGrrrl 
I was watching a trucking documentary online, and I wanted to know more about Mack and in particular, the Maxidyne. This was a very informative read, especially because it sounds like you have a lot of experience in the subject. Thanks.
Thank you for your well written account of these important historical events. To expound on the content, Mr. Pelizzoni was Chief Engineer at the Mack Trucks powertrain plant in Hagerstown, Maryland at the time. He not only invented the Maxidyne but guided his team of local engineers in developing the eventual product. The other gentleman was in the chain of command at Mack Trucks HQ in Allentown, Pennsylvania. He authorized the project and budget but made no technical contribution to it. People with ample experience in the corporate world are familiar with this process.
Those five speed maxitorque transmissions are unbeatable in urban stop and go driving
My dad, John Richard Crowe, retired in 1986 after 25 years of service, in the position of Chief Engineer of the Engine Development Lab. It was his invention that not only soved a gasket problem but also made developing and making the silver and the gold Maxidyne possible.
Drove mostly Mack’s in43 years of trucking, the one I still think about is 1980 R600 with a 300 Maxadyne with a 2 stick 6 speed (5 on one stick with low, direct reverse on the other). That truck pulled any hill it came across, and blew black smoke out its stack all the time. It was all Mack engine,transmission and rears.