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2003 - 2004 Ram 5.9L Cummins

The 2003 model year was the beginning of a new era for the Cummins Turbo Diesel, the Common Rail era. Dodge ditched the troublesome VP44 in favor of the more reliable Bosch CP3 injection pump, capable ... read more

Wheels & Tires

The 2003 model year was the beginning of a new era for the Cummins Turbo Diesel, the Common Rail era. Dodge ditched the troublesome VP44 in favor of the more reliable Bosch CP3 injection pump, capable of supplying fuel at up to 30,000 PSI to the rail. Besides the injection pump, common rail fuel systems feature electronically controlled injectors, and when it comes to power, efficiency, and performance tuning, this is an absolute game changer. Most Cummins enthusiasts would agree that this new system is easier to get big horsepower gains from, and all without sacrificing diesel fuel economy. The addition of the right tuner (our choice would be Smarty), a decent set of injectors, an upgraded turbo, some transmission modifications, a better fuel pump, some gauges to keep an eye on things, and these trucks will easily slip into the 500 RWHP range.


Beyond the engine upgrades, numerous changes were made to the rest of the powertrain, axles, body, and more at this same time. At the time of the release, the upcoming 48RE automatic transmission was not quite ready for market, thus Ram opted to not delay things and stuck with the previous 47RE that was found in the 1996-2002 model year 2nd Gens. Due to concerns over how much power these transmissions could handle, the early release iterations were derated below the 305 horsepower level that would be available in the manual transmission versions, and the later 48RE equipped trucks. Many would argue that the 48RE really wasn’t that big of an improvement over the 47RE, especially when you consider the waves GM was making with their Allison equipped trucks. Overall, the 48RE is a relatively lackluster option, but at least it can be easily upgraded to handle plenty of abuse.


Next up for discussion is in regards to the steering and suspension. In summary, its all different, but its all the same. Sounds weird, right? At least for the 2003 and 2004 trucks, all of the basic design and geometry was unchanged from the 2nd Generation Rams, but the physical parts are different and much of that honestly has to do with the fact that the “things” it all bolts up to changed, i.e. the frame and axles. Have you ever heard of a hydroformed frame? Ram opted to ditch the tried and true C-Channel style of frame and go with a completely boxed, hydroformed frame that is “bent” by using extremely high pressure water, instead of heat that causes weak points. The next big surprise was Ram moving away from Dana axles and giving the business to American Axle & Manufacturing, usually dubbed “AAM.”


For those of us driving an early 3rd Gen Ram, its kind of like having one toe into newer technology and a larger cab, but still wanting to keeping with a relatively “old school” truck that you can easily repair and upgrade. Whatever your goal is for your truck, whether it's big horsepower, better handling, or just keeping it on the road, we can help you out with name brands like Carli Suspension, BD Diesel Performance, Fleece Performance, Industrial Injection, South Bend Clutch, Dynomite Diesel, ISSPRO Gauges, FASS Fuel Systems, Mads Electronics Smarty Tuner, Edge, MBRP Exhaust, and much, much more.

NOTE: For those of you with 2004 model year trucks, it is important to understand that there are significant differences between a 2004 and a 2004.5. Different injectors, different turbos, different exhaust systems (2004.5 trucks have full 4" exhausts and catalytic converters), different valve bodies in the transmission etc. One way to check is to locate the red or silver tag on the driver's side of your block. On a 2004.5 the tag will show a torque rating of 600 or a horsepower rating of 325. 2004's will show a horsepower rating of 305. If you are still unsure call your local Dodge dealer with the last 8 #'s of your VIN and they can clarify it for you.

If you need help with your decision don't hesitate to call. Products in this section are designed to work on 2003 and 2004 model year Dodge trucks equipped with the 5.9L Cummins unless otherwise noted.

Diesel Power Products is not affiliated with Cummins or any of its subsidiaries or related companies. Unless a product is specifically identified as a Genuine Cummins product that has not been remanufactured, modified, or refurbished, Cummins makes no representation or warranty about the product and has not authorized, tested, or approved the parts for use in genuine Cummins brand products.

We get a lot of calls and e-mails each day with various product, vehicle, and installation questions. Some are completely off the wall and can even catch us off guard at times, but many others are fairly routine, so we thought we'd post some of the most popular questions that can hopefully be a good resource for you.

Q: How do you find out if your Cummins is a 2004.5 or a 2004?
A: There are two ways. First, you can check the drivers side of the valve cover at the estimated horsepower. If the truck is a 2004, it will indicate 305, whereas the 2004.5 models are rated at 325 horsepower. Secondly, early 2004 models (non-California) did not have a catalytic converter from the factory, where 2004.5 models do. If your exhaust is still original, this is an easy way to check.

Q: Do I need the Extreme Duty Red-Head Gear Box, or the regular unit?
A: The Extreme Duty is built for those running exceptionally large tires, such a a very wide 35" or a 37" or larger diameter. This model would also be a good idea for those vehicles whom regularly see off road use.

Q: I'm looking at an exhaust kit on your website, but it doesn't state which cab and bed configuration it fits, will this fit my application?
A: In most cases, unless it is specifically stated as fitting a certain configuration, all exhaust kits on our website will fit all cab and bed lengths. Further, most kits will not fit cab and chassis applications unless otherwise noted.

Q: I'm looking at this 5" (or other) exhaust kit, but my truck only has a 4" exhaust now. Does this 5" exhaust include an adapter / reducer?
A: Yes, the exhaust systems we sell will adapt down to fit the application at the designated starting point (turbo back, cat back, DPF back, etc.) for a hassle free installation.

Q: What are EGT's?
A: EGT stands for Exhaust Gas Temperature, which is the temperature of the exhaust leaving your engine. This measurement is typically measured before the turbo to ensure you are not overheating components. For most applications, we recommend not exceeding 1300 degrees.

If you've got a question about your Cummins, feel free to give us a call at 888-99-DIESEL and we would be happy to assist.

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