The 3rd Generation Ram 2500 and 3500 trucks — built from 2003 to 2009 — mark a turning point in diesel truck history.
This era brought together classic Cummins durability with modern refinement, giving us the beloved 5.9L and early 6.7L Cummins engines that still dominate the diesel scene today.
Whether you’re shopping for one or already own a 3rd Gen, here’s everything you need to know about this iconic platform — from drivetrain and performance to common issues, popular upgrades, and current market values.
Engine Overview: 5.9L and 6.7L Cummins
Two major engines powered the 3rd Gen Ram lineup:
2003–2007 5.9L Cummins (Common Rail)
The 5.9L 24-valve Cummins in 2003–2007 trucks was the first to use a Bosch common rail fuel system, providing smoother operation, better efficiency, and easier tuning potential than the older VP44 engines.
- Displacement: 5.9 liters (359 cubic inches)
- Fuel System: Bosch CP3 injection pump with solenoid injectors
- Output: 305–325 HP, 555–610 lb-ft torque (varied by year and trans)
Known for its simple mechanical design and long life, this engine has become legendary for reliability — capable of 400,000+ miles with proper care. It’s one of the most sought-after diesel engines ever built.
2007.5–2009 6.7L Cummins
In 2007.5, Ram introduced the 6.7L Cummins, bringing more torque and modern emissions systems.
Power increased to 350+ HP and 650 lb-ft of torque, and it became the first Cummins to use a factory variable-geometry turbocharger (VGT) and diesel particulate filter (DPF).
While stronger and more refined, early 6.7s had a few growing pains related to emissions controls — but many of these issues have been resolved through tuning and improved aftermarket parts.
Transmission Options
48RE Automatic (2003–2007)
The 48RE 4-speed automatic carried over from the 2nd Gen. It’s hydraulically controlled, relatively simple, and can be built to handle big power. However, in stock form, it’s limited in torque handling and can slip when tuned aggressively.
68RFE Automatic (2007.5–2009)
With the arrival of the 6.7L, Ram introduced the electronically controlled 68RFE 6-speed automatic. It provided smoother shifting and better fuel economy but wasn’t as strong internally as the 48RE when pushed beyond factory power levels. Built versions, however, can handle over 700 HP reliably.
G56 6-Speed Manual
Available throughout the 3rd Gen’s run, the G56 manual transmission remains a fan favorite. It gives drivers full control and incredible reliability — though it can suffer from input shaft flex or clutch wear under high power.
Many enthusiasts reinforce them with upgraded clutches.
Common 3rd Gen Cummins Problems
1. Lift Pump & Fuel Supply Issues
Stock lift pumps on 3rd Gen trucks (especially 5.9s) are known to fail or deliver inconsistent pressure, leading to premature CP3 or injector wear. Many owners upgrade to a FASS Fuel System to ensure constant pressure and filtration.
2. Injector Failures
High-pressure common rail injectors can stick or leak over time — especially if poor-quality fuel or filters are used. Symptoms include hard starts, white smoke, or excessive return flow.
3. Transmission Weak Points
Stock automatics can struggle with added power or towing abuse. Line pressure mods, torque converters, and valve body upgrades are common fixes.
4. 6.7L Emissions-Related Issues
Early DPF and EGR systems were prone to clogging, leading to high exhaust temps and poor fuel economy. Routine maintenance, updated calibrations, or compliant tuning solutions can improve reliability.
5. Steering & Suspension Wear
As trucks age, common issues include steering box play, track bar wear, and front-end wobble. Many owners upgrade to heavy-duty steering kits or Carli/PMF components to tighten things up.
Popular 3rd Gen Cummins Upgrades
- FASS Fuel Systems: Adds consistent pressure, air/vapor separation, and extended injector pump life.
- Turbo Upgrades: From drop-in turbos to full 2nd Gen swaps, these dramatically improve airflow and reliability.
- Tuning: Custom tuning via EFI Live and other platforms allows improved drivability and fuel efficiency.
- Suspension Kits: Carli, PMF, and BDS kits improve ride quality and stance.
- Steering Upgrades: Replacing worn factory front-end components can completely transform the way a 3rd Gen drives.
With these upgrades, a well-built 3rd Gen Cummins can easily surpass 500 HP while remaining a dependable daily or tow rig.
Current Market Prices (2025)
The 3rd Gen Cummins has officially reached “modern classic” status. Values remain strong thanks to their reputation and tunability:
- 2003–2005 5.9L trucks: $9,000–$40,000+ depending on mileage and condition
- 2006–2007 5.9L (last year of 5.9): $10,000–$40,000+ for clean examples
- 2007.5–2009 6.7L trucks: $9,000–$35,000, higher for low-mile or modified builds
“Unmolested” (stock) low-mile 5.9 trucks are particularly valuable, often fetching premium prices due to their reputation as the last of the simple, pre-emissions diesels.
Why Diesel Enthusiasts Love the 3rd Gen
The 3rd Gen Cummins strikes the perfect balance between old-school reliability and modern power. It’s simple enough for DIY mechanics, but capable of supporting serious performance builds.
Its timeless design, tunable powertrain, and mechanical integrity make it one of the most versatile diesel platforms ever produced.
FASS Motorsports: Your 3rd Gen Cummins Upgrade Experts
At FASS Motorsports in Washington, Missouri, we help owners of 3rd Gen Cummins trucks get the most from their builds.
From FASS Fuel Systems and suspension upgrades to wheels, tires, and tuning support (5.9 Cummins) — we have the products and expertise you need to keep your Cummins running strong.
👉 Shop 3rd Gen Cummins parts online
👉 Visit our Franklin County, MO showroom for professional installation & expert advice
Questions? We’re Here to Help.
- Phone: (636) 429-7020
- Email: info@fassmotorsports.com
FASS Motorsports
25 Town and Country Drive
Washington, MO 63090