Ram 6.4 Hemi Problems: Lifter Failure, Hemi Tick & Reliability Explained (2014-2025)

The Ram 6.4L Hemi V8, also known as the 392, is a celebrated engine, powering Ram’s 2500 and 3500 Heavy Duty trucks since 2014. It’s lauded for its impressive 410 horsepower and 429 lb-ft of torque, offering a potent gasoline alternative to the more expensive Cummins diesel. However, this engine’s service record is marked by a severe and widely documented design flaw.

This expert, data-driven report synthesizes technical service bulletins, owner data, mechanic reports, and legal filings to provide a definitive guide to the most common Ram 6.4 Hemi problems.

Part 1: Ram 6.4 Hemi Problems: The 5-Minute Executive Summary

For owners or prospective buyers needing immediate answers, the 6.4 Hemi’s problems are specific and significant. The most common and severe issues are (1) catastrophic lifter and camshaft failure, notoriously known as the “Hemi Tick,” and (2) broken exhaust manifold bolts, which create a separate, distinct ticking sound.

The primary engine failure, lifter and camshaft destruction, is directly linked to the engine’s Multi-Displacement System (MDS). This cylinder-deactivation technology, designed to improve fuel economy, can lead to insufficient oiling of the valvetrain components, resulting in their failure.

Secondary issues include a high failure rate for the 66RFE 6-speed automatic transmission in 2014-2018 models and numerous owner reports of excessive oil consumption.

The following table outlines the most critical issues owners and buyers face.

Top Problems Affecting the Ram 6.4 Hemi

Part 2: The “Hemi Tick” Explained: Differentiating Two Different Ticks

The single most confusing issue for 6.4 Hemi owners is the “Hemi Tick.” This ambiguous term is used to describe two vastly different problems, one of which is a minor annoyance while the other is a financial catastrophe. Misdiagnosing the tick can lead to thousands of dollars in unnecessary repairs or, worse, a complete engine failure that could have been prevented.

A) The “Bad Tick”: Lifter & Camshaft Failure (The $9,000 Problem)

This is the dreaded, engine-killing “Hemi Tick.”

• Symptom Deep Dive: This sound is a deep, internal, metallic knock or tap. It is the sound of a hardened steel lifter roller failing and grinding against the camshaft lobe. It is consistent and often gets louder or more pronounced as the engine warms up, unlike the exhaust tick.
• The Failure Progression: This failure occurs in predictable stages:
  1. Starts as a Tick: A faint metallic noise begins, often intermittently.
  2. Becomes a Misfire: As the lifter roller seizes, it fails to follow the cam lobe, preventing the valve from opening properly. This starves the cylinder of air, causing a misfire and triggering a Check Engine Light (CEL). Owners frequently report misfire codes on a single cylinder, such as a P0305 (Cylinder 5 Misfire).
  3. Catastrophic Failure: If ignored, the seized lifter and destroyed camshaft lobe send metal shavings and “glitter” (as one owner described it) throughout the entire oiling system. This contaminates the entire engine, turning a top-end repair into a complete engine replacement.

B) The “Common Tick”: Exhaust Manifold Leak (The $1,600 Problem)

This is the far more common, less severe “Hemi Tick,” which is not an internal engine problem.

• Symptom Deep Dive: This sound is a lighter, rhythmic puffing or ticking sound, sometimes compared to a sewing machine. It is simply the sound of exhaust gas escaping through a small gap between the manifold and the cylinder head.
• The Key Diagnostic Sign: It is almost always loudest on a cold start and will often disappear or get significantly quieter as the engine warms up. This is the critical difference. As the metal components heat up, the warped manifold expands, temporarily re-sealing the leak and silencing the tick.
• The Cause: This is a persistent design flaw. The engine’s cast-iron exhaust manifold and aluminum cylinder head expand and contract at different rates during heat cycles. This, combined with what mechanics call “subpar factory hardware” (weak bolts), causes the manifold to warp and the bolts to snap.
• The Fix: The repair involves replacing the broken bolts (which often requires drilling them out of the head) and, if the manifold is too warped, replacing it as well.

Part 3: The Root Cause: Why the 6.4 Hemi’s MDS System Is the Villain

The “Bad Tick” is not a random mechanical failure. It is a systemic problem rooted in the design of the engine’s valvetrain, specifically the Multi-Displacement System (MDS).

What is the Multi-Displacement System (MDS)?

MDS is Chrysler’s (now Stellantis) cylinder-deactivation system. It is designed to meet increasingly strict corporate average fuel economy (CAFE) standards. Under light-load conditions, such as cruising on a flat highway, the system deactivates four of the eight cylinders (S3, S39).

It accomplishes this using eight special, complex hydraulic “MDS lifters.” When activated by a solenoid, these lifters “collapse” internally, allowing the pushrod to remain stationary while the lifter continues to ride on the camshaft, thus preventing the valve from opening.

The MDS Oiling Flaw: How It Destroys the Camshaft

The consensus among independent mechanics and engine builders is that this MDS system is the root cause of the lifter failure. It introduces complexity and, more importantly, a critical oiling deficiency.

The failure mechanism is a direct result of oil starvation:

1. The Design Flaw: The valvetrain’s oiling passages are designed to support the MDS. A critical finding is that “oil flow to the rocker arms, pushrods, and lifters is restricted by the MDS solenoids when the system is in its off position”.¹ This means that in 8-cylinder mode—especially at low-RPM, such as idling—the lifters are not receiving the full, high-pressure flow of oil they need.
2. The “Idle is the Killer” Problem: This design flaw directly explains why mechanics and owners overwhelmingly identify excessive idling as the primary culprit for lifter failure. A truck left to idle for extended periods is operating in a low-RPM, low-oil-pressure state that by design restricts oil from the very components that need it most.
3. The Breakdown: The needle bearings inside the lifter’s roller are starved of lubrication and begin to seize.¹
4. The “Tick”: The seized roller stops rolling and begins to drag or skip across the hardened camshaft lobe, creating the metallic “tick”.
5. The End: This grinding action quickly destroys the camshaft lobe, and the lifter itself fails. Metal particles are then circulated by the oil pump, leading to catastrophic engine damage.

The Official Acknowledgment: TSB S1709000010 Rev. A

This problem is not just a theory from forums. The manufacturer, FCA, has acknowledged it in NHTSA Technical Service Bulletin S1709000010 Rev. A.

This TSB, issued to dealers, explicitly addresses customer complaints of “abnormal engine noise, rough idle, lack of power, [or] misfire” and instructs technicians on how to proceed if they find “excessive camshaft lobe wear/lifter wear (roller failure)”.

Crucially, the TSB’s diagnostic step validates the severity of the failure:

• Technicians are instructed to remove the Oil Control Valve (OCV) for the VVT system and inspect its screens for metal debris.
• If no debris is found, the technician is to replace the camshaft and lifters.
• If debris is found, the TSB states that “Engine replacement is required”.

This document serves as the “smoking gun,” confirming that FCA is aware of the lifter-failure-to-engine-failure pathway.

Part 4: The 6.4 Hemi Lawsuit: What Owners Need to Know

Owners searching for a recall on this issue will not find one. While recalls exist for Ram 2500 trucks—notably for software issues or for the heater grid on Cummins diesel models—there is no active safety recall for the 6.4 Hemi’s lifter and camshaft failure.

This lack of a recall, which leaves owners to pay for the $7,000 to $12,000+ repair out-of-pocket once the warranty expires, is the primary driver behind multiple class-action lawsuits.

The most prominent case is Petro, et al. v. FCA US LLC (Case No. 1:22-cv-00621-VAC).

• The Allegation: The lawsuit, which covers both 5.7L and 6.4L Hemi engines, alleges that FCA knew about this valvetrain defect since at least 2012 but actively concealed it. It claims FCA failed to disclose the defect to customers and has not provided an adequate or permanent fix.
• The “Safety Risk” Claim: The suit argues this is not merely a noise or cost issue, but a critical safety risk. The alleged defect can cause vehicles to “buck, surge, misfire… and result in catastrophic engine failure,” which severely compromises a driver’s ability to control the vehicle’s speed and increases the risk of a collision.

For owners facing this issue, the lawsuit and lemon law experts represent potential, albeit slow-moving, avenues for compensation.

Part 5: Secondary 6.4 Hemi Problems: Transmissions & Oil Consumption

Beyond the primary engine flaw, prospective buyers must analyze two other significant factors: transmission reliability and oil consumption.

A) Transmission Reliability: A Tale of Two Transmissions

A buyer asking for the “most reliable 6.4 Hemi year” is often unknowingly asking about the transmission. While the engine’s lifter-failure risk is consistent across all model years, the powertrain’s overall reliability was drastically changed in 2019.

The “Bad” Years (2014-2018): The 66RFE Transmission

From 2014 to 2018, the 6.4 Hemi was paired with the 6-speed 66RFE automatic transmission. This transmission is a known weak point, especially when subjected to the high-performance demands of the Hemi.

Common 66RFE failures include:

• Torque converter shuddering at highway speeds or complete failure.
• High-pressure oil pump leaks, leading to harsh or inconsistent shifts.
• Valve body cross-leaks and solenoid issues.
• Catastrophic failure requiring a full replacement.

This is not a cheap fix. One Ram Power Wagon owner reported a catastrophic failure at 92,000 miles with a dealer replacement quote of $17,000. Another had one replaced under warranty at just 40,000 miles.

The “Good” Years (2019-Present): The 8HP75 Transmission

In 2019, Ram Heavy Duty trucks with the 6.4 Hemi received a massive upgrade: the ZF-sourced 8-speed 8HP75-LCV automatic transmission.

This transmission is almost universally praised by mechanics and owners. It is described as “vastly superior in every way” and “a reliable strong transmission”. It provides a better driving experience, smoother power delivery, and has proven far more durable than its 6-speed predecessor.

This change means that any 2019-or-newer 6.4 Hemi truck is a significantly more reliable powertrain, even though the engine’s lifter risk remains.

B) Excessive Oil Consumption & Piston Scuffing

A separate but widespread complaint among 6.4 Hemi owners is excessive oil consumption. Owners report engines “burning” or “using” significant amounts of oil, with some needing to add a full quart or more between 5,000-mile oil changes.

One owner of a 2023 Ram 2500 reported their first 6.4 Hemi engine was replaced under warranty at 14,000 miles for this very issue, only to find the new engine was also consuming oil.

While some oil consumption is considered “normal” by manufacturers, the levels reported by 6.4 Hemi owners are often excessive. The cause is not definitively known but is sometimes linked to minor piston scuffing or issues with valve seals or piston rings related to the MDS system’s operation. A 2021 TSB (S119) related to PCM software causing high oil temperatures suggests the manufacturer is aware of oil-related issues in these engines.

Part 6: Solutions & Costs: How to Prevent or Fix 6.4 Hemi Problems

For current or future owners, the lifter failure problem can be managed, mitigated, or permanently fixed. The solutions range from zero-cost preventative habits to a full-on mechanical “MDS delete.”

Level 1 (Good): The Preventative Maintenance Plan (For ALL Owners)

This is the non-negotiable, baseline care required to minimize the risk of lifter failure.

1. KILL YOUR IDLE TIME: This is the single most important preventative measure. As established, extended idling creates the low-oil-pressure, low-flow state that starves the lifters.¹ This is especially critical for work trucks or any vehicle that sees significant idle time.
2. AGGRESSIVE OIL CHANGES: Do not follow the 10,000-mile (or longer) oil life monitor. The consensus from mechanics and informed owners is to change the oil and filter every 5,000 miles, max. Clean oil is critical to the health of these sensitive hydraulic components.
3. USE THE RIGHT OIL: Use a high-quality, full-synthetic oil that meets the manufacturer’s specification (Pennzoil Platinum is often SRT-approved).

Level 2 (Better): Proactive Upgrades (The “Hemi Tick” Prevention Plan)

For owners who want to be proactive without tearing the engine apart, two upgrades are highly recommended.

1. Install a High-Volume Oil Pump:
   • The Upgrade: A popular and effective upgrade is replacing the stock 6.4 Hemi oil pump with the higher-volume Mopar “Hellcat” oil pump (Part # 68195993AD).
   • The Benefit: This pump is a direct-fit replacement for 2009+ Hemi engines. It moves significantly more oil, especially at idle and low RPMs, forcing lubrication to the valvetrain and counteracting the MDS design’s starvation effect.
   • The Cost: While the part itself is relatively affordable, the labor is intensive as it requires accessing the engine’s timing cover. Owners can expect a total repair cost in the range of $1,500 to $2,100.
2. Disable MDS (The “Easy” Way):
   • The Method: On 8-speed (2019+) models, many owners manually “disable” the MDS for daily driving by using the +/- gear-limiter buttons on the steering wheel, which takes the transmission out of its fully automatic, MDS-engaging mode.
   • The Tuner: A more permanent software solution is to use a plug-in tuner (like a Diablosport or HP Tuner) to turn off the MDS function in the engine’s computer.

Level 3 (Best): The Permanent “MDS Delete” (The “Hemi Tick” Cure)

This is the only 100% permanent solution. It involves mechanically removing all MDS components from the engine and is the gold standard for long-term reliability. If you’re already paying for a lifter/cam replacement, performing a full MDS delete is the only logical path.

A full MDS delete kit and installation requires the following:

• 16 Non-MDS Lifters: The 16 complex hydraulic lifters (8 MDS, 8 standard) are all replaced with a full set of 16 simpler, more robust non-MDS lifters, such as the Mopar “Hellcat” lifters (Part # 5038784AD).
• New Camshaft: If your cam is already damaged (which is why you’re doing the repair), it must be replaced. If not, many owners swap it for a non-MDS cam profile anyway.
• MDS Solenoid Plugs: Plugs are used to block the oil passages in the engine block that once fed the (now-removed) MDS solenoids.
• New Gaskets & Bolts: The job requires new head gaskets, valve cover gaskets, timing cover gaskets, and head bolts.
• A Required ECU Tune: The engine’s computer must be reprogrammed with a tuner to permanently disable the MDS system, otherwise it will throw error codes and run improperly.

Cost: This is effectively a top-end engine rebuild. Parts-only kits range from $1,100 to $1,600+. A full professional installation will be significantly more, but it permanently solves the engine’s primary design flaw. If you are already this deep into the engine, it’s an excellent time to consider other upgrades. For more ideas, see our guide to Ram 2500 Performance Mods.

Part 7: 6.4 Hemi vs. The Competition (Ford 7.3L & GM 6.6L)

A prospective buyer, understandably concerned about the 6.4 Hemi’s lifter problem, will inevitably ask, “Should I just buy a Ford or a Chevy instead?”.

While the competition appears to offer an escape, the “grass isn’t greener.” A comparative analysis reveals that Ford’s 7.3L “Godzilla” V8—introduced to compete directly with the 6.4 Hemi—suffers from its own version of the exact same problem.

The Ford 7.3L “Godzilla” V8, while a simpler pushrod design, uses a variable-displacement oil pump. Mechanic analysis shows this pump can provide as little as 8 PSI of oil pressure at idle. This low idle pressure is, like the Hemi’s MDS flaw, reportedly starving the valvetrain and leading to widespread lifter and camshaft failures in the 7.3L, with some owners experiencing catastrophic failure at 132,000 or 140,000 miles.

The GM 6.6L L8T V8, by contrast, is a more “old-school” design (though it has direct injection) and is generally viewed as having higher reliability, though it also has reports of oil consumption.

Heavy-Duty Gas V8 Problem Comparison

This comparison shows that the 6.4 Hemi’s flaw, while serious, is not unique in the market. The real decision often comes down to other factors. For a deeper analysis of the Hemi’s capabilities, see our 6.4 Hemi vs. 6.7 Cummins Towing & Reliability breakdown.

Part 8: Final Verdict: Is the Ram 6.4 Hemi a Good Engine?

Based on a complete analysis of its service history, the Ram 6.4 Hemi is a powerful and capable engine, conditionally.

The engine’s core components—the block, crankshaft, and rotating assembly—are robust and well-built. Many owners, particularly those who follow strict maintenance or have disabled the MDS, report 150,000 to 200,000+ trouble-free miles.

However, the engine is saddled with a significant, well-documented design flaw in its MDS and valvetrain oiling system. This flaw introduces a major risk of failure that is not a guarantee, but is prevalent enough to be “a well known issue” and the subject of TSBs and class-action lawsuits.

Therefore, any recommendation must be split by model year.

Recommendation for Buyers

• New or Used (2019-Present):Recommended, with a caveat. This is the only era to consider. These models pair the 6.4 Hemi with the excellent 8-speed 8HP75 transmission, creating a far superior and more reliable powertrain. A buyer should purchase this truck with the full intention of either:
  1. Following the preventative maintenance plan (no idling, 5k oil changes) religiously.
  2. Proactively budgeting for a high-volume “Hellcat” oil pump or a permanent,mechanic-installed MDS-delete kit.
• Used (2014-2018): High Risk. Not Recommended. A buyer of this model is purchasing two major, expensive, and well-documented liabilities: the 6.4 Hemi lifter-failure risk and the problematic 66RFE transmission-failure risk. This truck should only be considered if the price is exceptionally low, allowing for a $15,000 – $20,000+ budget for a potential transmission rebuild and a necessary MDS-delete repair.

These known issues will certainly have an impact on the vehicle’s long-term cost of ownership. For a complete picture, see our analysis on Ram 2500 Resale Value & Depreciation.

Part 9: Frequently Asked Questions (FAQ)

What are the first signs of 6.4 Hemi lifter failure?

The first sign is a deep, metallic ticking or tapping noise from the engine. This is different from the lighter, “puffing” tick of an exhaust leak. This noise may be followed by a rough idle and a Check Engine Light for a misfire on a specific cylinder.

How much does it cost to fix the “Hemi Tick”?

This depends on which “tick” you have. An exhaust manifold leak (the “common tick”) can cost between $120 for DIY parts and $1,600 for a professional repair. The lifter/camshaft failure (the “bad tick”) is a major engine repair, with dealer quotes ranging from $7,200 to $9,000. If the failure is catastrophic and sends metal through the engine, a full engine replacement can exceed $12,000.

Can I prevent 6.4 Hemi lifter failure?

You can drastically reduce the risk. The best methods are: 1) Limit engine idling to an absolute minimum, and 2) Change the oil every 5,000 miles with a high-quality full synthetic. Proactive upgrades include installing a high-volume “Hellcat” oil pump or performing a full, permanent “MDS delete”.

What year 6.4 Hemi is the most reliable?

Any model from 2019 or newer is considered more reliable. This is not because the engine’s lifter-failure risk was fixed. It is because these models use the far superior and more durable 8-speed 8HP75 transmission instead of the problematic 6-speed 66RFE found in 2014-2018 models.

Does disabling MDS on a 6.4 Hemi really work?

Yes. Disabling the MDS system with a software tuner and, ideally, mechanically replacing the complex MDS lifters with simpler, non-MDS lifters is considered the only permanent fix for the lifter failure problem.

Is the 6.4 Hemi a good engine?

It is a very strong and capable engine at its core, with many owners reaching over 200,000 miles. However, it is built with one major, well-documented design flaw (the MDS lifters and oiling system) that must be addressed with strict preventative maintenance or proactive repairs.

What is TSB S1709000010 Rev. A?

This is an official Technical Service Bulletin from FCA (Chrysler) distributed to its dealers. It confirms the manufacturer is aware of the “excessive camshaft lobe wear/lifter wear” problem and provides technicians with diagnostic steps, which include inspecting for metal debris and, if found, replacing the entire engine.