Rearview Mirror: How Cummins Diesel Engines Saved Dodge Trucks

The first diesel-powered Ram truck arrived in 1989, but the car and motorcycle company had already worked together

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In 1939, Dodge completely redesigned and built its truck range in a brand new facility that was the largest truck factory in the world at the time. It also made its own diesel engine, which it dropped in its heavier models.

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Diesel engines were rare in all trucks, and this one only lasted a few years. Then fast forward to 1978, when Dodge offered its light trucks with an optional diesel from Mitsubishi, as Chrysler owned a stake in that Japanese automaker. That too was short-lived. Instead, continued success came in 1989, when Dodge equipped its heavy-duty Ram trucks with a Cummins engine.

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The diesel engine dates back to 1893, when the German engineer Rudolf Diesel patented his design for it. It was much more efficient than a steam engine and, compared to the rudimentary gas engines of the time, produced the same amount of power, but consumed much less fuel. Its large stationary diesel engines were used in industry, but even when small versions were developed, there was not much interest from automakers.

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Enter Clessie Cummins. Born in Indiana in 1888, he was fascinated by machines and reportedly built a small, working steam engine when he was only twelve years old. In 1908, he was hired as a driver by a banker, who later financed Cummins so that he could open an auto repair shop.

1989 Cummins 5.9L diesel
1989 Cummins 5.9L diesel Photo by Stellantis

Cummins thought there was a future in diesel engines that other companies ignored. Shortly after he founded the Cummins Engine Company in 1919, he produced his first, a six-horsepower single-cylinder diesel engine. After Cummins solved technical problems with his designs—and later nearly sold his company to General Motors—cars with his engines entered the Indy 500; a single-powered truck made a publicity ride from New York to Los Angeles on eleven dollars of fuel; and Cummins engines powered many of the military trucks in World War II. In 1939, when most vehicles were sold with a 90-day warranty, Cummins covered its engines for 100,000 miles (160,000 km). Clessie Cummins retired from his business in 1951 and died in 1968.

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Dodge didn’t have a huge share of the truck market and didn’t update its offerings very often. The 1961 models remained virtually unchanged until 1972, and That generation has struggled for over a decade. In the mid-1980s, sales plummeted and something had to be done. Dodge decided that a new engine would shake things up.

The 1989 trucks looked the same as before, but the three-quarter, one-ton trucks could now be fitted with a 5.9L Cummins inline-six diesel. GM and Ford offered diesels, but only the Cummins was turbocharged and had direct injection. It delivered 400 lb-ft of torque, while Chevrolet’s 6.2L V8 made a max of 248 lb-ft, and Ford’s Navistar-sourced 7.3L V8 produced 345 lb-ft of torque.

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Cummins has been making the engine since 1984, selling it primarily to farm and construction equipment companies. Dodge had to strengthen the truck’s frame and suspension and upgrade the cooling system to handle the heavy engine.

The 2007 Ram was delivered to customers with a tank of B5 biodiesel
The 2007 Ram was delivered to customers with a tank of B5 biodiesel Photo by Stellantis

Dodge sold 17,000 of the diesel truck that first year and could have fulfilled another 10,000 orders if it had the extra production capacity. By 1991, it had rolled 100,000 diesel-equipped pickups off the assembly line.

Prior to diesel, Dodge truck sales were in free fall. Rumor has it that the automaker was considering getting out of the truck business in general. It still didn’t outperform its Detroit rivals in sales, but within the first few years after the engine was available, half of all Dodge trucks made went out with a Cummins under the hood. Many appreciate the diesel for saving the automaker’s truck division.

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The choice for Cummins did not come out of the blue. Dodge had made a few big trucks from the 1930s onward, and in the 1960s was producing tilt cab trucks on the highway with Cummins engines. It closed that side of its business in 1975. Ford and General Motors also had large truck divisions, and both used Cummins diesel engines in some models.

Ram announces 865 lb-ft of torque for 2015
Ram announces 865 lb-ft of torque for 2015 Photo by Stellantis

Dodge completely updated its pickup trucks for 1994 with unmistakable big-truck styling, and it proved popular enough that Ram sales tripled the previous year. The Cummins stayed, updated with a new, higher-pressure fuel injection pump to meet stricter emissions standards, and torque up to 420 lb-ft.

Then Ford updated its diesel to 425 lb-ft, and the torque wars were on. Cummins upgraded the Ram for 1998 with a new 5.9L diesel with 24 valves, good for 460 lb-ft of torque. Ford responded quickly with 500 lb-ft, so Dodge’s diesel was modified to 505 lb-ft.

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2018 Ram 5500 Chassis Cab Crew Cab 4×4 with 6.7L Cummins Engine
2018 Ram 5500 Chassis Cab Crew Cab 4×4 with 6.7L Cummins Engine Photo by Stellantis

In 2007, Ram switched to a new 6.7L engine, rated at 350 horsepower and 650 lb-ft of torque on its debut. To meet emissions regulations, it was Cummins’ first engine with EGR (exhaust gas recirculation) and a diesel particulate filter. Ram’s heavy-duty models still use a 6.7L inline-six today.

You can track the power development: Ram had 930 lb-ft in 2018, while Ford had 935 lb-ft. Ram went to 1,000 lb-ft in 2019; Ford adjusted to 1,050 lb-ft in 2020; and so Ram went to 1075 lb-ft in 2021. While Ford hasn’t revved up its engine yet, it’s probably just a matter of time. (GM, capped at 910 lb-ft, tends to sit back and let the other two fight it out.)

In 2008, Dodge announced that its “post 2009” light 1500 would get an all-new Cummins turbo diesel engine. It never happened. Chrysler went bankrupt in 2009 during the financial crisis and came out as part of Fiat. The Ram 1500’s 3.0L V6 EcoDiesel, introduced for 2014, came instead from Italian supplier VM Motori. Yet the relationship with Cummins, at least for heavy work, remains very much alive.


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