America has witnessed its fair share of legendary business partnerships, from Henry Ford and James Couzens at Ford Motor Company, to Ben Cohen and Jerry Greenfield of Ben & Jerry’s, and of course, Microsoft’s Bill Gates and Paul Allen. However, few partnerships have shaped an industry quite like that of Dodge and Cummins. Call it a match made in diesel heaven. Cummins diesel engines sit so well into Dodge (now Ram) trucks that the name Cummins has become synonymous with Ram diesel power. What you might not know is that Cummins wasn’t always part of the picture.
In the late 1970s and early 1980s, the United States experienced a sudden surge in diesel truck demand, primarily driven by fuel shortages and high prices following the 1973 oil embargo. Diesel engines offered better torque and improved fuel efficiency compared to gasoline engines. But while Dodge’s main competitors, Ford and General Motors, were already making headway with in-house diesel engines for their trucks, Dodge was exploring outsourcing options.
At the time, Chrysler owned 15% of Mitsubishi, so it only made sense to tap into the Japanese automaker’s diesel expertise. Dodge settled for the Mitsubishi 6DR5, a naturally aspirated 4-liter inline-six diesel engine capable of 105 hp and 169 lb-ft of torque.
Pre-Cummins engines in Dodge trucks
Before settling for its first diesel engine, the 6DR5 inline-six from Mitsubishi, Dodge also featured some Gasoline engines in its pickup trucks, including the Dodge LA-series V8 engines, and specifically the 318 (5.2-liter V8) and 360 (5.9-liter V8). While both engines were known for their durability and performance, the 360 was favored for its high output (longer bore and stroke). Dodge also used big blocks like the 400 and 440 cubic-inch V8s in its 3/4-ton (D200 model) and 1-ton (D300 model) line of trucks. The 440 cubic inch was a particularly powerful engine and replaced the 400, finding its way into several Dodge vehicles, including muscle cars.
In the early 1980s, Dodge briefly had its first diesel attempt – the 6DR5 inline-six (243 cubic-inch) Mitsubishi engine. It was a naturally aspirated 4-liter diesel engine. Dodge used the same transmissions (manual and automatic) used in the LA-series V8, incorporating an adapter plate that fit into the LA V8 bolt pattern. While it was what Dodge was looking for in terms of fuel efficiency, it was severely underpowered for the American pickup truck market, delivering 105 horsepower.
During this time, Ford and GM were already offering more established and potentially stronger diesel engines in their trucks compared to Dodge. While GM and Dodge were first in line to offer diesel pickups in 1978 (Ford followed in 1983), Dodge’s initial engine offering was short-lived. They did not introduce another engine until 1989 with the 5.9-liter 12-valve Cummins B-series engine.
The 1989 Cummins switch up
In 1989, Dodge partnered with Cummins and debuted the 5.9-liter 12-valve inline-6 turbo diesel. This collaboration was a game-changer for Dodge, with the diesel engines finding a home in the D/W250 and D/W350 models. The 5.9-liter Cummins turbodiesel engine was capable of 160 hp and 400 lb-ft of torque, a significant improvement over the Mitsubishi 6DR5, offering better towing and durability.
The Cummins 6BT (12-valve 5.9-liter inline-6) was based on commercial trucks, and for that reason, it was designed to last. Compared to its competition, it featured direct injection and turbocharging, making it far superior. The 6BT won legions of fans when it first appeared in the D-Series trucks in 1989.
And even though several other trucks have been produced ever since the first Cummins was stuffed into a Dodge truck, diesel enthusiasts won’t let go of the 6BT. This is because in its standard form, the 5.9-liter Cummins was quite capable and could be tuned to produce up to four figures.
