What year are 2nd gen Cummins?

The second-generation Cummins refers to the 5.9-liter inline-six diesel used in Ram pickups from late 1998 (the 1999 model year) through 2002.

Gen II: The years it covered

Below is a concise timeline of when the second-generation Cummins 24-valve engine appeared and the model years it powered in Dodge Ram heavy-duty pickups.

• Introduction in late 1998 for the 1999 model year, marking the switch from the 12-valve Gen I to the 24-valve Gen II.


• Primary production years for Gen II: model years 1999–2002 in Dodge Ram 2500/3500 pickups.


• End of Gen II era: 2002 served as the final year for the widely recognized Gen II 5.9L Ram Cummins; starting with the 2003 model year, Dodge began using a different fuel-injection system often referred to as a CR (common-rail) setup, which some enthusiasts classify as a separate generation.

In short, Gen II spanned roughly the 1999–2002 model years, with the late-1998 introduction marking the transition from the prior generation.

How to tell Gen II from Gen I

Use these quick identifiers to distinguish the second-generation 24-valve Cummins from the earlier 12-valve Gen I engines.

• Engine design: Gen II uses a 24-valve cylinder head (4 valves per cylinder) versus the Gen I’s 12-valve configuration.


• Model years and appearance: Gen II appeared in Dodge Ram 2500/3500 pickups starting with late 1998 production for the 1999 model year.


• Fuel and emission setup: Gen II introduced updates to fuel delivery and emission-control strategies to meet evolving standards, distinct from the earlier 12-valve setup.


• Identification marks: The engine badge/cover and data plate on Gen II-ran trucks will indicate the 5.9L 24V Cummins designation, differentiating it from the Gen I 12V engine.

Understanding these differences helps buyers, enthusiasts, and restorers identify which Cummins is under the hood and plan maintenance or upgrades accordingly.

Why this matters for owners and buyers

For owners and prospective buyers, the Gen II window defines which parts, service manuals, and upgrade options are compatible. The 24-valve design offers improved airflow and potential for higher reliability with proper maintenance, while the subsequent CR-equipped engines from 2003 onward represent the next evolutionary step in Cummins diesel technology.

Summary

The second-generation Cummins in Dodge Ram trucks spans the 1999–2002 model years, with the late-1998 introduction signaling the shift from the Gen I 12-valve design. This era is defined by the 24-valve 5.9L Cummins and its associated updates, followed by the transition to new fuel-injection technology in the 2003 model year. For anyone working with these trucks, knowing the Gen II window helps ensure accurate part compatibility and maintenance planning.

What year are the 2nd gen Cummins?

1994 to 2002
As the 5.9-liter Cummins diesel engine quickly established itself as a superior powerplant for Dodge Ram rigs in 1989 to 2001 trucks, the term "2nd-Gen Cummins" became the regularly used blanket moniker for 1994 to 2002 rigs, despite "Gen" being more associated with the truck than the engine.

What year are 3rd gen Cummins?

The 3rd generation Cummins engines are found in Dodge trucks from model years 2003 to 2009. The 5.9L engine was used from 2003 to early 2007, and the newer 6.7L engine was introduced in 2007 and used through the 2009 model year.
 

• 2003-2007: These years feature the 5.9L high-pressure common rail engine. 
• 2007-2009: These later models include the larger 6.7L engine. 
• Note: Some trucks built in 2007 may have either the 5.9L or 6.7L engine depending on their build date. 

What is the holy grail of Cummins?

The "holy grail" Cummins is typically a 1994-1998 12-valve Cummins engine with the P7100 injection pump, particularly when paired with a rare quad cab and a rare 5-speed manual transmission (NV4500). These are considered the "holy grail" because this era combines the engine's reputation for reliability with a highly desirable and hard-to-find body and drivetrain configuration. 
Key characteristics of a "holy grail" Cummins

• Engine: The 12-valve, 5.9L Cummins engine produced between 1994 and 1998, known for its reliable mechanical P7100 injection pump.
• Transmission: The rare combination of a 5-speed manual NV4500 transmission, as they are much harder to find than the automatic versions.
• Body: The quad cab configuration is highly sought after, as it was first introduced in 1998, the last year for the 12-valve engine.
• Combination: The most desirable version is a 1998 quad cab with the 12-valve engine and a manual transmission, a rare combination that is very difficult to find in good condition. 

Other "holy grail" models

• Some enthusiasts consider the late 2001.5 and 2002 second-generation trucks to be a "holy grail" due to their increased horsepower, improved automatic transmission, and rear disc brakes. 
• In some cases, a highly modified truck, even if it's not from the 1994-1998 era, can be called a "holy grail" because of the extensive and expensive work put into it. 

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What year is 5.9 Cummins to avoid?

You should avoid 5.9 Cummins years with known weaknesses, specifically 1998.5–2002 (due to the unreliable VP44 injection pump and potential lift pump failure) and 1999–2001 (due to the "53 block" casting, which is prone to cracking). While other years may have specific issues, these are the most frequently cited for potential major failures. 
Specific years and common problems to avoid:

• 1999–2001: These are the most critical years to avoid due to the "53 block" casting with thin water jacket walls that can lead to cracking and coolant leaks. 
• 1998.5–2002: These models use the Bosch VP44 injection pump, which is prone to failure. A failure in the lift pump that feeds the injection pump can cause a chain reaction, leading to the expensive VP44 failing as well. 
• 2004.5–2005: These models have injectors that were more prone to premature wear, which can lead to rough starts, smoke, or fuel in the oil. 

Other considerations:

• Transmission: The 47RE automatic transmission, found in 1994-2002 trucks, is a weak point due to its older design and smaller components. 
• 1998: This year is a bit of a transition year, but can still have the VP44 injection pump issues mentioned above. 

Years considered more reliable:

• 1994–1998: These 12-valve engines are highly reliable due to their mechanical P7100 injection pump.
• 2006–2007: The last of the 5.9L common rail engines are considered by some to be the peak of 5.9L performance before the introduction of the 6.7L.