Ram Tough, Cummins-Powered
Probably the biggest single factor that moved recognition of the Cummins name beyond the commercial truck sector was the company's partnership with Chrysler. By the mid-1980s, Chrysler was the only one of the Detroit Three automakers that did not offer a diesel option in its full-size trucks. General Motors was first, offering a diesel in its full-size trucks starting in 1978. Ford followed by offering a diesel sourced from International Harvester in 1983. Both of these engines were naturally aspirated V-8s and offered power comparable to their smaller-displacement gasoline counterparts with better fuel efficiency, but neither was particularly known for its torque output, characteristic of today’s modern turbodiesels .
Dodge was at an added disadvantage because it had one of the oldest truck designs at the time, with the basic styling dating back to 1972. The trucks received a refresh in 1981, when the Ram badge was first officially applied to the truck line, but they had no remarkable features in particular that stood out relative to newer competitors from General Motors and Ford. Dodge had previously offered a diesel in the Ram's D-series predecessor in 1978 in the form of a 4.0-liter naturally aspirated Mitsubishi inline-six. The engine was economical, but produced only 105 hp and 169 lb-ft of torque and was considered woefully underpowered. It was offered for just one model year. If Dodge was going to have a breakout hit, it was clear it needed to have something unique in the marketplace.
That standout feature would come in the form of the Cummins B-series six-cylinder engine. Cummins had already established a rock-solid reputation in the commercial segment and the company was ready to set the stage for its next level of growth. John Keele, Cummins' OEM marketing manager at the time, shared his insight on the early stages of development of the Cummins-powered Ram. "In early 1981, Chrysler formed Truck Operations to breathe new life into its truck division. During the same year, Cummins began marketing the new medium-duty engine line," Keele said. "Cummins then invited Chrysler to review its B series engine and its market research and engineering facilities.
In 1983, Cummins requested the engine compartment drawings to check fitment of the 5.9L B-series under the hood. From there, a running mock-up engine was shipped to Chrysler for use in a demonstration vehicle. After the technical review of the truck and the realization that there were no major issues, the project was kicked off formally."
Getting the B-Series into the Ram was no shade-tree engine swap. Because the Cummins engine was substantially longer and heavier than the 360 cubic-inch V-8 that was the Ram’s top engine and also produced substantially more torque, Dodge had to relocate the radiator support forward by 4 inches, use a larger radiator and add an engine oil cooler. Additional upgrades included a new electrical system, strengthened transmission (and new torque converter) better suited for the diesel's low-end torque, beefier rear axle, and upgraded transfer case and axle shafts for the four-wheel-drive models.
With potential output well above 200 hp and 500 lb-ft in commercial applications, the engine had to be detuned for use in the Ram. Taking into consideration emissions regulations, driveline strength and reliability, the final calibration for the 1989 Ram was 160 hp and 400 lb-ft of torque.
Although the horsepower was around the same as that offered by the naturally aspirated diesel V-8s at the time from GM and Ford, the torque figure positively crushed them. Because the engine was designed for much heavier-duty use than it would ever see in a pickup, it enabled the Ram to have a substantial payload and towing advantage over its rivals. The seeds of the diesel truck performance revolution had been planted.
Don Altermatt, chief engineer of Diesel Products for Chrysler, has worked closely with Cummins since joining the company in 1994. From the early exploratory phases of the joint-venture between the two companies, the joint team has grown into a tight-knit collaboration of mutual respect and an intense focus on delivering the best product to the customer. "Our working relationship is very strong. We work from a technical perspective as if we're one company. The engineering teams meet daily, literally, and the senior management teams meet two to four times a year. We're pretty well-integrated and work very well together." Altermatt said. "What I personally enjoy from the perspective of the technical team is that it's all about the customer. It's all about protecting our joint customers. It's not about Cummins and it's not about Chrysler, it's about our customers."
This customer-driven model has guided the collaboration and development of products that deliver the attributes truck buyers want and need, which in the three-quarter and one-ton truck sector is primarily fuel economy and reliability. Although Cummins has very advanced R&D resources and capabilities, the team won't put an unproven product on the market. "Cummins is very much cutting-edge in its understanding and research. But it’s certainly not introducing technology for technology's sake," Altermatt said.
Cummins may not be a deliberate trend-setter, but its thorough focus on diesel development gave it an early edge in the HD truck segment. One example is the the multi-valve ISB engine introduced in 1998, three model years before competitors would offer the same feature. That same basic architecture has formed the basis for the engines offered in the Ram HD since, with the biggest change coming in 2007, with a displacement increase from 5.9 to 6.7 liters. This would bring output to a substantial 350 hp and 650 lb-ft of torque. Although Ford and GM were now in the ballpark in terms of power, Dodge and Cummins still enjoyed the best reputation for reliable, trouble-free operation.
1000 lb-ft Future?
With a figure that would have been inconceivable only a few years ago, the soon-to-be-introduced 2013 Ram HD models equipped with the Cummins and the Aisin six-speed automatic now produce 385 hp and a massive 850 lb-ft of torque. The idea that we would be approaching the 1000-lb-ft mark in a factory diesel pickup is mind-blowing, but we're now probably only a few years away from it. Whatever your truck brand preference is, we can thank Clessie Cummins and his tireless determination, and that fortuitous conversation between central Indiana and suburban Detroit for the diesel pickup performance scene we have today.
Allpar.com – Clessie Lyle Cummins and Cummins Diesel Engines by Curtis Redgap
Allpar.com – Cummins 5.9 liter and 6.7 liter Inline Six-Cylinder Diesel Engines by Curtis Redgap
"The Diesel Odyssey of Clessie Cummins" by C. Lyle Cummins, Carnot Press, 1998