With its unveiling in 2005, the 6.4L HEMI engine by Chrysler became the option to go for if you wanted horsepower and torque that was on an extreme level.
It has held up pretty well over the years. As beefy as the engine may be, the engine indeed has some flaws that you should know about.
I will be outlining some of the RAM 6.4 HEMI problems below:
- Failure Of The MDS
- Failing Spark Plugs
- Failure Of The Transmission System
- Ticking Sound From The engine
I wrote a whole article on the 5.7 Hemi engine, and most of the problems over here are similar to the ones that had too. That is rather interesting. Regardless, I assure you that these issues are fixable. So, without any further ado, let’s jump straight into it!
The 4 Most Common RAM 6.4 HEMI Problems
We will now be diverting our attention to the problems I listed above. We will be going into the depth of each one of these issues.
1. Failure Of The MDS
What is more frightening than an issue that suddenly emerges? You guessed it, one that slowly affects it and is barely noticeable too. The MDS system is a relatively new technology implemented into Chrysler engines.
It is responsible for shutting down four cylinders when there is not a high-power requirement. In theory, this is great for people who want to save fuel when not needed.
So, what can go wrong with a system that has been designed to boost efficiency? Well, the manufacturer did not take into account the rapid temperature changes. Metal does not respond well to temperature variations. This directly affects the cylinders, which can wear off quickly and unevenly.
That is not all. When a cylinder shuts down, the associating spark plug is also not needed. If the MDS system determines that there is power usage and the cylinders are turned on, the sudden change in temperature of the spark plugs may affect them. They can and have failed on users due to this issue.
Although the technology has been around for more than a decade, there have not been any changes to address these issues. But there are a few things that can be used to identify if the MDS is causing issues with the engine:
- Failing spark plugs.
- Misfire issue.
- Rough idling.
Now, these issues can be caused due to various reasons. But if they are happening together, then there is a high chance that MDS is causing issues.
So, what can be done to avoid the issue? The simplest answer is to disable the system entirely. You will be sacrificing fuel efficiency, but it is much better for the engine in the long term. If the issue has damaged the cylinders and the spark plugs, then, unfortunately, they will need to be replaced.
2. Failing Spark Plugs
Reason For The Problem
I did mention misfires as a symptom of the problem above. It turns out that is only one of the many reasons that can cause the engine to misfire. With the 6.4L engine having 16 spark plugs, there is a very high chance of one or more failing before the other. This is mainly due to the MDS system.
But spark plugs can fail due to excessive usage too. When engines have been used extensively, the spark plugs will fail. After all, they are not meant to be used forever. The ignition coils can also cause the issue, as they are subject to the same wear and tear as spark plugs.
Ignition coils can also fail, but they are likely to survive twice as long as the spark plugs. That is why we are focusing on the latter. Fortunately, there are a few things that you definitely cannot miss or overlook that confirm the presence of faulty spark plugs:
- Hesitation while accelerating.
- Starting issues.
- Rough idle.
If all of the above symptoms are happening at once, then there is a high probability that the spark plugs fail. If they are, then it is recommended not to drive the vehicle any further. You should get it towed to the nearest workshop as soon as possible to get the issue diagnosed and sorted out.
New spark plugs do not cost a lot. So, you can get them replaced easily. If you go to a mechanic, then you will be charged a hefty labor fee. Another alternative is to perform the job yourself! You will not only be saving money, but you will also be satisfied with the work.
3. Failure Of The Transmission System
We will now be discussing the most critical problem of all, the unexpected failure of an engine’s transmission system. The transmission system is an essential part of an engine, without which a vehicle is rendered useless.
Before you start reading, I must tell you that the issue is the least common of all four and has a high chance of happening to a specific group of people more.
As expected, with almost all sorts of failures, the transmission system gives up when exposed to too much wear and tear. This happens on all engines, but it usually occurs in the end stages of an engine’s life. But with the 6.4L HEMI engine, the issue occurs too frequently.
The problem was also faced by users of the Ram 2500 and the 3500. It was present in others too, but it was more frequent on these vehicles.
Many people use their trucks for towing, especially the beefy 6.4L engine; one can naturally expect the transmission system to handle the strain. But unfortunately, the users who bought this engine thought wrong. The transmission failure was commonly due to the excess strain on the system due to towing.
Symptoms And Repair
A faulty transmission system cannot go unnoticed. There are many symptoms of it becoming faulty, with the most common ones being:
- Missing gears.
- Rough shifting while driving.
- Engine emitting clunking sounds.
Unlike symptoms of other problems, all of this guarantees that the transmission system has failed or is failing on you. At this point, there are no repairs present for this issue.
The only thing you can do is get the whole transmission replaced. It will cost you a lot, but that is the only way to get your vehicle back in usable condition.
4. Ticking Sound From The Engine
I saved the most interesting one for last. A ticking sound that emerges from the engine is more of a symptom rather than a problem. Many users of the HEMI engine reported this issue, so it deserved a spot on this article.
If you read about the problem, you must know that there are many conflicting answers online. Now, some experts say that the ticking sound is harmless and will not cause any damage to the engine.
In contrast, some people had to get their whole engines replaced due to this issue. I will be providing a definitive answer.
Source Of The Issue
So, what does cause this ticking sound from the engine? After extensive research, I found out that there are two possible reasons for the engine to start emitting this annoying ticking sound:
- Failure of the lifters.
- Stuck lifter rollers.
Surprisingly, this was the exact issue with the 5.7L HEMI engine. Some people have claimed that the reason for this issue is the MDS system, which has been proven to cause issues before.
If the rollers stop working, the lifters will make contact with the camshaft lobe constantly. This will result in a ticking sound.
Effect On The Engine
So, what does this issue do to the engine? Apart from the sound, which is very annoying, the constant metal contact may produce shavings that enter the oil. Here the oil filter becomes very useful. It will stop the larger shavings, but over time the engine will be affected.
The issue can be resolved as soon as the sound is heard. The rollers can be replaced, but the procedure will cost you a lot. The bill may exceed the cost of a new remanufactured engine, so I recommend going for that option instead.
What Is The 6.4 HEMI Engine?
In 2005, Chrysler unveiled this beast of an engine to the world. The engine, when under production, was codenamed Apache. It was featured in its very first vehicle in 2011. In between that time, it was a crate engine. You could order it and install it in your vehicles with the appropriate modifications.
Even by today’s standards, the 6.4 HEMI engine could output a whopping 525 HP, which is mind-blowing. That was quite a big gap between the unveiling and first use. Regardless, people fell in love with the engine, not only due to the improved horsepower but due to its durability too.
There is one interesting thing to note. The engine shipped with the vehicles did not have all the parts similar to the crate engine. Plus, the former also had lesser HP, all while it is advertised as the same product.
Is The 6.4 HEMI Engine Reliable?
The HEMI engine is not even close to being one of the most reliable engines on the market. But it still is pretty reliable. With it being featured in many mainstream, heavy-duty vehicles, the engine is indeed great for any type of task.
The engine will provide you with all the HP you need to get a smooth and fantastic driving experience from towing to off-roading.
No matter how reliable the engine is, there are always faults that ship with it. In the case of this one, four issues plagued users. But they can be avoided with the proper maintenance and check-ups.
You have to use high-quality oils and get any issues fixed as soon as possible, and there is a chance that you can get more than 200000 miles from this engine. This is plenty of mileage for an engine, but only the proper care will let you achieve that.
What Cars Use The 6.4L HEMI Engine?
I did tell you before that although the engine was unveiled in 2005 until 2011, it was only a crate engine. 2011 saw the Dodge Challenger SRT8 unveiled with this bad boy under the hood.
The SRT 392 and the R/T Scat Pack feature this engine under the hoods. The same models of the Dodge Charger ship with this engine too.
Other vehicles with this engine are the Chrysler 300 SRT, the Jeep Grand Cherokee SRT, and the Dodge Durango SRT. All of these are pretty popular vehicles, and the fact that the company used the engine in such a way means that there is something special about it.
But no vehicle can defeat the popularity of the RAM series. Yes, you guessed it, the RAM 2500 and the 3500 ship with the same engine. They are also available with other engines, but this 6.4L one is considered one of the best.
6.4L HEMI Engine Specs
|Cylinder block composition||Cast iron|
|Chamber head composition||Aluminum|
|Fuel injection type||Sequential multi-port injection|
|No. of chambers||8|
|Valves in each cylinder||2|
|Bore||103.9 mm or 4.09 cubic inches|
|Stroke||94.6mm or 3.72 cubic inches|
|Displacement||5.2L or 6407 cc|
|Internal combustion engine (Type)||Four stroke, Naturally articulated|
|Compression ratio||10.9:1 – HEMI SRT, 10.0:1 – HEMI RAM Trucks|
|Power||366-485 HP @ 4100 rpm|
|Torque||429-475ft.lb @ 4000 rpm|
|Weight of engine oil||SAE 0W-40|
|The capacity of engine oil||7 quarts w / filter|
|The interval between oil change||6000 miles (10000km) or six months|
The Benefits Of Choosing The 6.4L HEMI Engine
Let’s change the pace and talk about the benefits of owning the engine. After all, it is a pretty popular option. The 6.4L HEMI engine has many upsides, which you will love.
Apart from the excellent driving experience, some of the advantages of owning this engine are:
- The engine delivers torque at a low speed while retaining fuel efficiency.
- Thanks to new construction material, the weight of the engine was also reduced.
- The MDS system turns off four cylinders to greatly reduce fuel consumption.
- The crankshaft has been made from forged steel and has increased rolling pressures.
- As compared to the 6.1L predecessor, the compression ratio was improved too.
- There is even a variable cam timing that enables improved airflow.
Frequently Asked Questions
If you have some questions, then I suggest that you read this part of the article in its entirety. It may clear up some of your confusion.
Online forums contain answers from all sorts of people, amateurs, and experts. It is difficult to get a solid answer. These questions have been researched thoroughly to give you a short and precise answer.
Q1. Is The 6.4L HEMI A Good Engine?
Whether you are talking about the crate engine or the modified one that shipped with the engine, I can assure you that the engine is not good, but it is great.
The 500+ HP is enough to make anyone happy. It does have some issues, but they are all repairable. The 6.4 HEMI engine will provide you with a pleasant driving experience.
Q2. What Kind Of Gas Mileage Does The 6.4 HEMI Get?
For this answer, we will be taking the example of the latest and greatest 2020 Ram 2500. After considering and testing everything, including the MDS system, the engine ended up with an average of 15.4 mpg. That is very impressive for an engine of this size and power. Chrysler outdid itself.
Q3. Can The Gas Mileage On The 6.4 HEMI Be Improved?
I honestly don’t know why you would tweak the engine to get better mileage. The 15mpg average is just fine. But there are a few things that you can do to give you some improvements. The engine could be tuned, better-quality oil can be used, and the engine’s weight or the vehicle can be reduced.
Q4. Does 6.4 Liter HEMI Require Premium Gas?
Yes, it does. For the engine to reach its maximum capacity, there needs to be high-quality fuel in the tank. The HEMI will take the 91 Octane fuel only. Any other will cause a drop in performance and fuel efficiency. Now, you don’t want that.
Q5. What Is The Best Spark Plug For The 6.4 HEMI?
The 392 engine is prone to spark plug failure; we talked about that in the article. You need to get replacements that are even better and will handle abuse easily.
The ones that check the boxes are the 6510 NGK Iridium spark plugs. They have been designed for the HEMI engine and are the best spark plugs money can buy.
I understand if many of you are hesitant about the engine after reading this article. After all, the RAM 6.4 HEMI problems are no joke.
The engine requires extreme care, but it will provide you with an unparalleled driving experience. If you keep the engine maintained at all times, and you also make sure that any problems are fixed as soon as they appear, then you will not have to worry about anything.
With the engine still in production, as of 2021, even the manufacturer will be willing to fix the issues if they appear. I hope that this article may have influenced your decision on whether to purchase the 6.4L engine or not. It is a great one, like all Chrysler engines.
Hi there! I am Tahir Azam, and this is my blog. WVDOT Automotive is a website dedicated to creating high-quality content for car enthusiasts. I am also an avid car driver. I own and drive a Porsche for my daily tasks. It is the perfect vehicle for my family. I am a proud father of two boys. I spend my mornings and evenings catering to clients at my very own software hub. After getting home, I dedicate a few hours of my time to creating an article every day. Well, this is a short introduction about me and I am also a publisher on Amazon. I hope you enjoy reading through my articles, and I also hope that I may have helped you choose an upgrade for your vehicle.