T3 Exhaust Manifold for 5.9 Cummins 2003–2007 | 2-Piece Expansion Design | 3rd Gen | CARB Exempt
The Diesel Power Source® T3 exhaust manifold for 2003–2007 Dodge Ram 2500 and 3500 trucks with the 5.9L common rail Cummins engine is a direct bolt-on replacement that flows 23% more than the factory manifold and lowers rear cylinder EGTs by up to 200°F. This 2-piece expansion joint design is cast from high-nickel moly-bendum ductile iron, CFD designed and flow-tested, and includes drilled and tapped ports for pyrometer and boost pressure fittings. It replaces OEM part numbers 5135788AB, 5135788AC, and 4931223.
This manifold is CARB exempt with an Executive Order (EO) number, making it legal for installation and street use in California. The factory heat shield is removed during installation as it is no longer necessary with the DPS manifold design.
Why the Stock 3rd Gen Manifold Fails
The factory 2003–2007 5.9 Cummins exhaust manifold is a single-piece casting that shrinks significantly over time from repeated thermal cycling. This shrinkage causes manifold cracking, gasket failures, and exhaust port misalignment where the manifold ports shift out of alignment with the cylinder head ports. Once this happens, exhaust leaks form, turbo efficiency drops, EGTs climb, and the rear cylinders run dramatically hotter than the center cylinders. Replacing a cracked stock manifold with another single-piece casting simply restarts the same failure cycle.
The DPS 2-piece expansion joint design solves this by allowing the manifold to expand and contract with heat instead of fighting it. The expansion joint absorbs thermal stress, eliminating the warping, cracking, and port misalignment that destroy factory and single-piece aftermarket manifolds.
Why Runner Size Matters
Some competitor manifolds advertise oversized runners or large tube designs. While this sounds appealing, runners that are too large actually slow exhaust gas velocity. The exhaust then has to re-accelerate as it bottlenecks through the turbo flange, causing a loss in horsepower and turbo spool-up. DPS has tested competitor manifolds with oversized runners that decreased horsepower by 40 HP on a 400 HP truck.
The DPS manifold uses CFD-tested runner geometry that maintains exhaust velocity from the ports through the collector while flowing 23% more volume than stock. The runners are balanced so that end-port EGTs are much closer to center-port EGTs, reducing the hot spots that cause manifold cracking and gasket failures.
Specifications
| Specification | Value |
|---|---|
| Design | 2-piece expansion joint |
| Material | High-nickel moly-bendum ductile iron |
| Flow Improvement | 23% more than stock |
| Rear Cylinder EGT Reduction | Up to 200°F |
| Turbo Flange | T3 (factory bolt-on) |
| Coating | High-temperature ceramic (1,400°F rated) |
| Pyrometer Ports | Drilled and tapped (pyro and boost pressure) |
| CARB Status | Exempt (EO numbered) |
| OEM Replacement | 5135788AB, 5135788AC, 4931223 |
| Included Hardware | Block gaskets and two bolts |
| Fitment | 2003–2007 5.9L common rail Cummins (3rd gen) |
DPS 2-Piece Ductile Iron vs Stainless Steel Manifolds
| Feature | DPS 2-Piece Ductile Iron | Stainless Steel Manifolds |
|---|---|---|
| Thermal Expansion | Minimal — ductile iron expands less than stainless | Expands up to 2x more than ductile iron |
| Cracking | Expansion joint absorbs thermal stress | Welds and rigid sections prone to cracking |
| Head/Gasket Stress | Low — expansion joint flexes independently | High — expansion transfers stress to head, gaskets, bolts |
| Leak Risk | Low — less flange movement | Higher — gasket sealing issues from expansion |
| Longevity | Designed for long-term thermal cycling | Can fatigue faster under repeated cycles |
What's Included
- DPS 2-piece T3 exhaust manifold for 3rd gen 5.9L Common Rail Cummins
- High-temperature ceramic coating
Optional upgrades (Available Above):
- Complete Hardware & Gasket Kit — adds the MLS manifold gaskets, stud-and-nut mounting hardware, and turbo install components for both factory HE351CW and aftermarket S300-style T3 turbos.
Installation Notes: Hardware in the upgrade kit fits both the factory HE351CW and aftermarket S300-style T3 turbos — no need to specify your turbo at checkout. The DPS manifold is thicker than the stock manifold, so the Complete Hardware & Gasket Kit is recommended for proper turbo mounting depth — included if you select the upgrade above.
Key Features
- 23% More Flow Than Stock — CFD designed and flow-tested
- Up to 200°F Lower Rear Cylinder EGTs — Balanced flow across all six cylinders
- 2-Piece Expansion Joint Design — Eliminates cracking, warping, and port misalignment
- High-Nickel Moly-Bendum Ductile Iron — Handles extreme heat with minimal expansion
- CARB Exempt (EO Numbered) — Legal for use in California
- Direct Factory Bolt-On — T3 flange matches factory manifold and turbo location
- Drilled and Tapped Ports — Pyrometer and boost pressure ready
- Balanced Runner Design — End-port EGTs closer to center-port temps
- Ceramic Coated — High-temperature coating for heat management
Black High-Temperature Coating
DPS exhaust manifolds are finished with a high-temperature black ceramic coating designed to handle extreme heat and real-world diesel performance conditions. This coating is rated for sustained temperatures up to 1,400°F, helping reduce surface heat, improve durability, and maintain a clean appearance under normal operating conditions. Because exhaust gas temperatures can vary significantly depending on tuning, load, and driving conditions, appearance changes may occur if those temperatures are exceeded.
Please note: The black ceramic coating is rated for temperatures up to 1,400°F. If exhaust gas temperatures exceed approximately 1,470°F, the coating may discolor and shift to a gray appearance. This is a normal result of excessive heat exposure and does not affect the performance or structural integrity of the manifold. Warranty does not cover coating discoloration or finish changes due to high EGT conditions.
About the Manifold Joint Seal
Every DPS multi-piece manifold uses a hard, metal-to-metal press-fit seal at each joint — no gasket. The seal tightens through thermal expansion and performs best at driving temperatures (750°F and higher). Minor leakage at cold or idle is normal and expected on any joint-style manifold and is not a sign of a defective part.
Every manifold is pressure-tested leak-free at room temperature before it leaves our facility. For a full explanation of how the seal works, why soapy-water idle tests aren't a valid diagnostic, and how the multi-piece design outlasts single-piece manifolds, see:
Understanding DPS Multi-Piece Exhaust Manifolds →
Real-World Results
Customers consistently report faster turbo spool-up, smoother acceleration, and lower EGTs after installing this manifold. One customer reported gaining 2 PSI of boost simply from swapping to the DPS manifold with no other changes. The improved exhaust flow and balanced cylinder temperatures make this one of the best first modifications for any 3rd gen 5.9 Cummins that tows or works hard.
OEM Cross-Reference
This DPS T3 exhaust manifold replaces the following OEM part numbers for the 2003–2007 5.9L common rail Cummins:
- 5135788AB
- 5135788AC
- 4931223
Fitment
This manifold fits 2003, 2004, 2005, 2006, and 2007 Dodge Ram 2500 and 3500 trucks with the 5.9L common rail Cummins engine. Direct factory bolt-on replacement with T3 turbo flange.
RV, Bus, and Commercial Applications
This manifold also fits RV, motorhome, school bus, and commercial vehicle applications equipped with the 5.9L common rail Cummins engine (2003–2007 build dates). The T3 flange and head bolt pattern are identical to the Dodge Ram application. If your RV or bus has a cracked or leaking factory manifold, this DPS 2-piece design provides the same 23% flow improvement and crack-resistant expansion joint construction. Contact Diesel Power Source® if you need fitment confirmation for a non-Ram application.
Have a 24V truck (1998.5–2002)? See the T3 Exhaust Manifold for 24V Cummins 1998.5–2002.
Have a 12V truck (1989–1998)? See the T3 Exhaust Manifold for 12V Cummins 1989–1998.
Have a 6.7L truck (2007.5–2018)? See the T4i Exhaust Manifold for 6.7 Cummins.
Related 5.9 Cummins Products
Factory manifolds are prone to warping and cracking and can create unnecessary backpressure. A performance manifold uses smoother runners, a divided T3 outlet, and heavy-duty cast material to flow better and handle heat cycles.
This manifold flows 23% more than the factory manifold and lowers rear cylinder EGTs by up to 200°F. Customers consistently report faster turbo spool-up, smoother acceleration, and measurably lower EGTs. One customer gained 2 PSI of boost from the manifold swap alone with no other changes. This is one of the best first modifications for any 3rd gen that tows or works hard.
Yes. It’s designed for 2003–2007 5.9 Cummins trucks with a T3-based turbo. Always confirm your turbo flange before ordering.
Fresh gaskets and high-quality hardware are recommended with any manifold install. Reuse only if they are in excellent condition.
The factory manifold is a single-piece casting that shrinks over time from thermal cycling, causing cracking, gasket failures, and exhaust port misalignment. The DPS 2-piece expansion joint design allows the manifold to expand and contract with heat instead of fighting it. The expansion joint absorbs thermal stress, eliminating the warping and cracking that destroy factory and single-piece aftermarket manifolds.
This DPS manifold replaces Cummins/Dodge part numbers 5135788AB, 5135788AC, and 4931223 for the 2003–2007 5.9L common rail Cummins engine.
Yes. This DPS exhaust manifold has been granted an exemption by CARB and carries an Executive Order (EO) number. It is legal for installation and street use in California.
Stainless steel expands up to 2x more than ductile iron during heat cycles. That extra expansion stresses the cylinder head, gaskets, and bolts, causing failures in those components. The DPS manifold uses high-nickel moly-bendum ductile iron with a 2-piece expansion joint that absorbs thermal movement without transferring stress. It stays tight, aligned, and built to last through thousands of heat cycles.
Yes. This manifold fits RV and bus applications equipped with the 5.9L common rail Cummins engine (2003–2007 build dates). It uses the same T3 flange and head bolt pattern as the Dodge Ram application.
22 Reviews
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Great Manifold
Good lookin manifold. Its nice that it comes with tapped ports for a pyrometer. Unable to monitor EGTs at the moment. Only issue I had with the manifold is the bottom stud on #5. Incredibly tight clearances between the manifold and nut making it near impossible to get a wrench or socket on it - i did though.... Other than that fitment and looks are nice!
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Great Manifold
Good lookin manifold. Its nice that it comes with tapped ports for a pyrometer. Unable to monitor EGTs at the moment. Only issue I had with the manifold is the bottom stud on #5. Incredibly tight clearances between the manifold and nut making it near impossible to get a wrench or socket on it - i did though.... Other than that fitment and looks are nice!
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5.9 3rd gen manifold
Very nice manifold. Bigger than stock. Just got done installing it. Pretty good difference over stock and sounds much better by giving the exhaust a lower tone.
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5.9 3rd gen manifold
Very nice manifold. Bigger than stock. Just got done installing it. Pretty good difference over stock and sounds much better by giving the exhaust a lower tone.
