5 Of The Most Powerful Diesel Engines Ever Put In A Dodge Truck

Michigan natives John and Horace Dodge broke into the budding automotive industry at the dawn of the 20th century as parts suppliers to the likes of Oldsmobile and Ford. They built their first vehicle in 1914, and by the following year, Dodge Brothers was the nation's third-biggest automaker. They soon added trucks and vans to their lineup,  and Chrysler bought Dodge in 1928. The famous ram hood ornament appeared on Dodge trucks in 1933, and by the late '40s, four-wheel drive and diesel engines had been added to the list of functional features. 

Dodge began using the Cummins 5.9 liter diesel engine in its pickups in 1989. For those first few years, the Cummins 5.9 produced 160 horsepower and 400 pound-feet of torque, although output would climb steadily as the pages of the calendar turned. Those changes gradually brought the 5.9 into the realm of the most potent diesel engines ever used in Dodge trucks. Dodge split Ram off into its own division in 2009, but for the purposes of cataloguing these engines, we'll keep Dodge and Ram branded trucks in the same bucket. Let's first explore how the 5.9-liter Cummins evolved and then see where it fits among the other potent diesels that have powered Dodge and Ram trucks.

The Cummins 5.9's 12-valve architecture was revamped for the second generation in 1994, and a new Bosch injection pump increased the fuel pressure.  To make the most of the increased diesel flow, the injectors, pistons, and turbocharger were also upgraded. Halfway through the 1998 model year, the valve count was doubled to 24. This major change helped bump the engine's output to 215 horsepower and 420 pound-feet of torque when coupled to an automatic transmission, and 235 horses and 460 pound-feet in front of a stick shift. A high-output version of the 5.9-liter Cummins followed for the 2002 model year. That configuration provided 245 horsepower and 505 pound-feet of torque, but more major updates were still to come. 

The third-generation Cummins 5.9 engine appeared in 2003, with power numbers of 305 horsepower and 555 pound-feet of torque. That wasn't the last round of changes for this indomitable engine, though. Midway through the 2004 model year, another update came that increased those numbers to 325 horsepower and 610 pound-feet of torque. It's not just the capacity of this engine that changed over time. Early versions were susceptible to what's known as the "killer dowel pin" issue, where the alignment rod for the timing chain cover could come loose and wreck the engine. 5.9-liter Cummins engines made before 2002 were more likely to experience this failure, although the problem can be rectified with an $8.99 dowel pin replacement kit from Amazon.

When the 6.9-liter Cummins turbodiesel engine replaced the 5.7-liter version midway through the 2007 model year for Dodge Ram trucks, it brought cleaner emissions, quieter operation, and most importantly, more power. The cast-iron block and heads were carried over from the smaller engine, but redesigned fuel and air intake systems gave the new version significantly more grunt. The early iterations of the 6.7-liter engine produced 350 horsepower and between 650 and 800 pound-feet of torque. 

Dodge truck enthusiasts have burned countless electrons debating online which of these two Cummins diesel engines is superior, but based on output alone, the advantage definitely goes to the 6.7-liter version. That engine carried over the 24-valve system used in later 5.9-liter engines, also retaining the inline-six cylinder format. The 6.7-liter was the first diesel engine to power trucks that used the Ram name without the Dodge moniker in front. Like the earlier, smaller engine, the 6.7-liter Cummins diesel went through some major changes that increased its power output.

When the Cummins 6.7-liter I6 was upgraded midway through the 2013 model year, the changes were significant. Cummins' new emissions control system made the engine more fuel-efficient and doubled the recommended oil change interval to 15,000 miles, but most important were the power gains. Output climbed to 385 horsepower and between 850 and 865 pound-feet of torque, giving the 2015 Ram 3500 with the high-output Cummins diesel engine and Aisin six-speed automatic transmission a towing capacity of up to 30,000 pounds.

That's at least five tons more than the same truck with a manual transmission, which is rated for between roughly 13,000 and 18,500 pounds of towing depending on the rear axle's gear ratio. Payload capacity for those Ram 3500 trucks with the high-output engine was 6,580 pounds, while Ram 3500s with the lighter standard 6.7 Cummins could haul 140 pounds more. Another boost in torque and towing capacity was on the way for Ram truck owners, though.

The next upgrade of the 6.7-liter Cummins diesel engine came in 2018. Horsepower output stayed level at 385, but maximum torque for the high-output version jumped from 865 to 930 pound-feet. This diesel engine also had an exhaust brake, a feature usually found on commercial tractor-trailers that helps restrict airflow in order to keep the engine's speed low. This enables the driver to control their vehicle on downward grades, especially when pulling a trailer.

The added torque and engine braking capacity of the new high-output 6.7-liter engine gave the 2019 Ram 3500 HD a whopping 35,100 pounds of maximum towing capacity with the Aisin six-speed automatic transmission handling gear changes. Tom Quimby of Hard Working Trucks hooked a 2019 Ram Limited up to a trailer with a large farm tractor on it, and loaded the bed with logs. He described the truck's performance hauling this load as "just effortless," adding, "It really handled towing and hauling at the same time." Given a few more years to tweak things, Cummins and Dodge came up with an even more powerful engine-truck combination.

In 2021, Cummins upgraded the standard and high-output versions of its 6.7-liter I6 turbodiesel engine. When coupled with the Chrysler 68RFE automatic transmission, the standard version could now manage 370 horsepower and 850 pound-feet of torque. The high-output engine coupled with the Aisin six-speed automatic was capable of 420 horsepower and 1,075 pound-feet.

With this drivetrain, the 2024 Ram 3500 can tow an incredible 37,090 pounds. That's enough to pull eight 2025 Ford F-150s chained bumper-to-bumper, although this is not something we advise doing.

The latest Ram 3500 has more than just that powerful engine to make towing a breeze. It's available with an automatically leveling rear air suspension, which will adjust to the load and changing driving conditions. There's a trailer tire pressure monitoring system to help keep tabs on what you're pulling, and Ram will install a rear crossmember with a fifth-wheel hitch if you're going to tow that type of trailer.