2004.5-2007 Dodge 5.9L Cummins Exhaust Systems

Cat-back exhaust on the 2004.5-2007 RAM 5.9L Cummins

Starting with the 2004.5 trucks, the 5.9L Cummins came with a factory 4-inch exhaust and a catalytic converter downstream of the turbo. A cat-back replaces the pipe, muffler and tailpipe behind that converter. The converter stays. Cat-back kits for this truck are offered in aluminized or stainless construction, and the MBRP kits here come in 4-inch and 5-inch diameters.

What a cat-back will and won't do

It will change the sound, and it gives you a fresh system behind the converter. It won't add much power on a stock truck. On third-generation trucks the stock turbine housing is the biggest restriction in the exhaust, with pumping losses that are significant even at stock power, so changing the pipe alone gives little gain. Buy a cat-back for sound and appearance, or because you're replacing the pipe behind the converter anyway.

What we carry

• MBRP Armor Lite 4-inch cat-backs: S6108AL and S6108P.
• MBRP Armor Plus 4-inch cat-back: S6108409.
• MBRP Armor Lite 5-inch cat-backs: S61180AL, S61180P and S61180PLM.
• MBRP universal exhaust adapters.
• A Banks Power 53799 36-inch pipe kit made for Banks exhaust systems on 1998.5-2007 Cummins trucks.

Every MBRP cat-back in this list is listed for the 2004.5-2007 5.9L. Check each product page for the material and the cab and bed it fits. For other trucks, see our main exhaust page.

Fitment notes

Cab and bed length matter most here. Regular Cab, Quad Cab and Mega Cab trucks with a short or 8-foot bed use different tailpipe and over-axle sections, and most cat-backs list the cab and bed they fit. The year break matters too: 2003 and early 2004 trucks have a 3.5-inch downpipe with no converter, so check the build date on any 2004. On a 2007, confirm the 5.9L, since the 6.7L shared that model year with a different exhaust. Verify by VIN when in doubt.

Frequently asked questions

Should I pick a 4-inch or a 5-inch cat-back?

Both bolt on behind the factory converter. On a stock truck the turbine housing is the main restriction, so the bigger pipe won't change power much, and the choice comes down to sound and the look out back. Either way, make sure the kit lists your cab and bed.

Aluminized or stainless: which should I buy?

Cat-backs for this truck come both ways. Check the material on each MBRP product page and pick by where the truck lives and how long you plan to keep it. Either one keeps the factory converter in place.

Will a cat-back fit my Mega Cab?

Only if the kit lists it. Cab and bed length change the tailpipe and over-axle sections, so a Quad Cab short-bed kit won't automatically fit a Mega Cab. Read the fitment on the product page or use the fitment checker, and call us if it isn't clear.

Not sure what fits? Call the shop at the number in the header, or use the fitment checker on any product page. We install everything we sell.