Dodge RAMs have a well-documented history of bulletproof engines, and when lugging around a heavy-duty pickup truck, it’s one of the most useful assets you could have. An engine with enough torque to tow a small house, and for it to be reliable enough to outlast the truck itself. Even in the modern era, RAMs are considered very tough vehicles. The 2024 RAM 1500 received a quality and reliability rating of 89/100, proving that the legacy is living on, with far more complex engines.
One of the indestructible powertrains that truly showed the world its longevity was the 5.9-liter inline-six. And whilst the production run lasted in RAMs for 18 years (1989 to 2007) and saw several changes in its time, the intention and outcome were always the same. An engine that could do anything and do it forever. Truly a legend of the past which defies time and mileage, and with plenty of examples still acting as workhorses today, this is more true than ever.
What Makes This Engine So Indestructible?
The key to this engine’s dependability relies on a few significant factors, ones that we’re moving further away from in the modern era. Starting life as a powertrain that was intended for industrial equipment like tractors meant that it was designed to pull extremely heavy vehicles. Because of this, not only was the engine over-engineered in the first place with a plethora of cast iron and enormously strong components, but putting it in a pickup truck would mean the engine was being severely understressed compared to its original use case.
Despite being cast iron, most powertrains still suffer from the usual suspects, which bog down a diesel’s long-term strength. For one, modern chains and timing belts always need replacing after some time, and are always a risk factor even when correct maintenance is carried out. The 5.9-liter inline-six was gear-driven, a heavy-duty solution compared to alternatives, which snap or stretch. Not only that, but the connecting rods and bearings used were enormous compared to gasoline cars or even standard truck engines, making it easy to maintain consistent high-torque pressure.
Changes Over The Years To The Powertrain
The engine was first used in a Dodge RAM in 1989, and this iteration of the powertrain stayed similar until 1998. In 1994, they introduced the Bosch P7100 inline injection pump, which was insanely durable, marking the beginning of the truly bulletproof era. In those four years leading up to 1998, it was viewed as a true masterpiece. With the upgrade allowing for easy tunability and massive horsepower, and the durability still intact, this was very much the golden era for the engine.
Core Generations Of The 5.9-Liter Inline-Six
- 1989-1998 12-valve more mechanical engine
- 1998-2002 24-value ISB with electric fueling
- 2003-2007 shift to the 24-valve common rail
- 2004-2007 turbo update to push 610 Ib-ft of torque
Each of these iterations kept the fundamentals in place, but all had their own quirks. The first generation was incredibly simple and the most reliable, but lacked some of the huge torque later models produced. The 1998-2002 model saw the most issues due to the new electronic weakpoints, and the infamous VP44 pump; some were known for leaking coolant. By the time the run was coming to an end, though, they had ironed out most of the issues: better injectors and a superior high-pressure pump. This gave the 5.9-liter a strong final goodbye with excellent torque figures and legendary reliability.
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How This Engine Made The RAM A Legend
With Ford and Chevrolet being by far the most popular choices for pickups in the 1980s, Dodge had a lot of work to do. The 5.9-liter Cummins was more than a spectacular engine; it made the truck itself a force to be reckoned with. It became impossible to ignore. When people became aware that Dodge was moving to a 5.9-liter diesel engine made by Cummins, it surprised people and gave connotations of serious strength. And whilst petrol was the golden standard for trucks at the time, the 1989 Dodge RAM proved that it could haul loads that Ford’s struggled with at an effortless 1,700 RPM. This was the final generation of the 5.9-liter Cummins engine in the RAM, and allowed for extremely impressive specifications and a huge uplift in torque, whilst maintaining strength.
2005-2007 Dodge RAM 5.9-Liter Cummins Specs
|
Horsepower |
325 |
|
Torque |
610 Ib-ft |
|
Transmission |
4-speed automatic or 6-speed manual |
|
Towing Capacity |
13,000 – 14,000 pounds |
|
Payload |
2,600 (RAM 2500) 5,020 (RAM 3500) |
The Shift From The 5.9-Liter Cummins To The 6.7-Liter Monster
A more modern engine would go on to replace the 5.9 Cummins, a beast within itself. The 6.7-liter engine that would go on to carry RAM’s forward in 2007 would still offer incredible reliability, with examples reaching over 500,000 miles. Whilst that’s maybe not as shocking as the 5.9-liter’s acclaim for being part of the “million mile club”, half a million miles still points towards an incredibly designed engine. The 6.7-liter Cummins shares a lot in common with the 5.9-liter outgoing variant. Fortunately, the 6.7 used many of the same high-quality components of the 5.9, with its cast iron heart still being at the epicenter of its abilities.
The inline-six stayed almost exactly the same in layout, meaning it would continue the trend of the natural balance and lack of heavy vibration as the previous engine. Once the 5.9-liter had learned its lesson by using an extremely durable injection pump, the 6.7-liter continued this trend, sticking with the rock-solid Bosche CP3 pump. Ultimately, what killed the 5.9-liter in the Dodge was its poor emissions — it simply wasn’t cut out for the early move towards green measures in the mid 00s, and so they added an EGR and DPF filter to hugely improve emissions. Whilst these filters have been known to clog and cause reliability concerns, it was necessary to keep huge diesels on the road.
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The Verdict On The Legendary 5.9-Liter Cummins
The excellent 5.9-liter inline-six Cummins was more than just a tough engine; it redefined what a pickup could do. It wasn’t just a fairly powerful car with a towbar and a bed at the back — it was something which could pull loads several times heavier than the truck itself with ease, something that would shake up the boundaries of what was possible. And for Dodge, it well and truly cemented RAM on the map as the golden standard for heavy-duty users.
With RAM still thriving in more recent years, even with a shift to hybrid engines and a move away from diesel, it’s essential to remember that a big chunk of this success was down to that phenomenal and unstoppable, truly bulletproof cast-iron inline-six. And while emissions simply don’t allow for such engines to be produced now, we can still expect plenty of 5.9-liter RAMs on the roads for decades to come.
Sources: RAM, Dodge, J.D. Power