2003-2004 Dodge 5.9L Cummins Mufflers

Mufflers on the 2003-2004 Ram 5.9L Cummins

The factory exhaust on the common-rail 5.9L Cummins runs 3.5-inch pipe from the turbo to the front of the muffler and 4-inch pipe from the rear of the muffler to the tailpipe. The stock muffler handles that transition. Aftermarket 4-inch systems replace it with a straight-through muffler or a resonator, and the exact layout varies from one brand's kit to the next. The only emissions hardware on this engine is the oxidation catalytic converter, and a muffler change is cat-back work that leaves it in place.

Why change the muffler

The 3.5-inch stock section is restrictive on trucks with even mild upgrades or heavy towing. It raises drive pressure and EGT, and you notice it as high temperatures on grades and slow spool. Moving to a 4-inch or 5-inch cat-back system addresses that, and the muffler or resonator you pick is a big part of how the truck sounds when the job is done.

Choosing a muffler

Start with diameter. A 4-inch muffler matches the factory tailpipe size and a 4-inch system, and a 5-inch muffler goes with a 5-inch system. Then pick the style: MBRP offers Quiet Tone models, a high-flow Armor Plus muffler, universal 409 stainless mufflers, and resonators, including the Armor Lite resonator muffler. Finish the system with tips, which come polished or black.

What we carry

Every item here comes from MBRP, part of our larger exhaust section:

• Mufflers: universal 4-inch and 5-inch 409 stainless mufflers, the GP290022 Armor Plus 5-inch High Flow muffler, the Armor Lite 5-inch Quiet Tone muffler and the universal 4-inch Quiet Tone muffler.
• Resonators: MBRP diesel resonators in aluminized and stainless steel, and the M20681 Armor Lite resonator muffler.

Fitment notes

For the Dodge Ram 2500 and 3500 only, not the Ram 1500. These are universal mufflers, so check inlet and outlet size and body length against your system on the product page. On a full system, cab and bed length decide the tailpipe section, and MBRP lists 2003 and 2004 trucks under separate fitments, so verify by wheelbase. Use the fitment checker or call the shop in Wildwood, FL; we install everything we sell.

Frequently asked questions

Will a 4-inch muffler fit my stock 2003-2004 exhaust?

The factory pipe behind the muffler is 4-inch, but the pipe going into the stock muffler is 3.5-inch, because the muffler is where the size steps up. A 4-inch muffler drops into a 4-inch system cleanly; on stock pipe you have to account for that 3.5-inch inlet side.

Do I need a 5-inch muffler?

Only if you are running a 5-inch system. The factory tailpipe section is 4-inch, and 4-inch or 5-inch cat-back systems are the usual upgrade paths on these trucks. Match the muffler to the pipe you have or plan to install.

Why does the stock exhaust hold back a towing truck?

The 3.5-inch section from the turbo to the muffler is restrictive once a truck has even mild upgrades or tows heavy. It raises drive pressure and EGT, which shows up as high temperatures on grades and slow spool. A larger cat-back system with the right muffler opens that up.

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.