Introduction: A Change That Raises Eyebrows
Truck owners and diesel enthusiasts have long trusted Cummins for its legendary durability, but the 2019+ Cummins engine introduces a major shift: the replacement of traditional tappets with roller lifters. While this may seem like a modern engineering upgrade, the reality is far more complex. This change brings concerns about long-term reliability, potential failure points, and increased maintenance requirements. Let’s break down why this shift might be a step backward and what truck owners can do to stay ahead of potential issues.
Roller Lifters vs. Tappets: Key Differences
Traditional Flat Tappets: Simple and Reliable
For decades, Cummins engines have utilized flat tappets, which are simple in design yet highly effective. These tappets sit between the camshaft lobes and pushrods, providing direct and even force distribution. Their benefits include:
Proven durability over hundreds of thousands of miles
Robust, low-maintenance design
Ability to handle extreme loads with minimal wear
The New Roller Lifters: A Double-Edged Sword
The 2019+ Cummins engine replaces tappets with roller lifters, which incorporate a small wheel at the contact point with the camshaft. In theory, this reduces friction, leading to better efficiency. However, real-world implications suggest otherwise:
Increased Complexity: More moving parts mean more potential failure points.
Roller Bearings: A Weak Link? Tiny needle bearings inside the rollers are prone to failure, especially under high-load conditions.
Lubrication Sensitivity: Unlike tappets, roller lifters demand consistent and high-quality oil to prevent premature wear.
Why This Could Be a Step Backward
While roller lifters work well in high-revving gas engines, they present unique challenges in diesel applications:
1. Premature Bearing Failure
Roller lifters rely on needle bearings to function smoothly. If these bearings fail, the roller can seize, causing significant damage to the camshaft and even the engine block. Tappets, by contrast, don’t rely on bearings and typically wear down gradually rather than failing catastrophically.
2. High-Stress Diesel Environments
Diesel engines operate under immense pressure, and Cummins’ legendary reputation stems from its ability to handle extreme loads. The added complexity of roller lifters introduces a potential weak point, especially for owners who regularly tow or haul heavy loads.
3. Increased Maintenance Demands
Truck owners who are used to Cummins’ “set it and forget it” reliability may be in for a surprise. Roller lifters require:
Frequent oil changes with premium synthetic oil to prevent bearing wear
Closer monitoring for abnormal valvetrain noise that could signal impending failure
Potential aftermarket upgrades to reinforce weak components
Real-World Failure Points and Their Impact
Camshaft Wear and Spalling
One of the biggest concerns is excessive camshaft wear. If a roller lifter fails, it can lead to:
Pitting and gouging of cam lobes
Reduced engine performance and efficiency
Metal shavings contaminating the oil system, leading to further damage
Sudden Engine Failure Risks
Unlike tappets, which wear gradually, roller lifters can fail suddenly, leading to:
Engine misfires or power loss
Expensive repairs (new camshaft, lifters, and potential block damage)
Extended downtime for work trucks and fleet operators
How to Mitigate These Issues
1. Stick to a Strict Maintenance Routine
Since roller lifters are highly dependent on proper lubrication, use high-quality synthetic diesel oil and change it more frequently than Cummins’ recommended intervals.
2. Consider Aftermarket Solutions
Many aftermarket companies already offer upgraded roller lifters with reinforced needle bearings or even solid bushings to eliminate the weak points in OEM designs.
3. Monitor for Early Warning Signs
Pay close attention to valvetrain noise—ticking or knocking sounds could indicate lifter wear.
Perform regular oil analysis to check for metal contaminants.
Use high-zinc additives to improve camshaft and lifter longevity.
4. Tuning Adjustments
Some tuners may be able to adjust valvetrain geometry or modify oil pressure settings to better support roller lifters. However, this should be done carefully and only by professionals.
Final Thoughts: Should You Be Concerned?
The shift to roller lifters in the 2019+ Cummins engine is a mixed bag. While the goal was to reduce friction and improve efficiency, the real-world impact on durability remains questionable. Truck owners and diesel enthusiasts should approach this change with caution, staying proactive with maintenance and considering aftermarket upgrades to reinforce weak points.
If you depend on your truck for heavy-duty work, don’t wait until failure happens—take steps now to protect your investment and keep your Cummins running strong for years to come.