2003-2004 Dodge 5.9L Cummins Exhaust Systems

Exhaust pipe on the 2003-2004 Ram 5.9L Cummins

The common-rail 5.9L Cummins in these trucks feeds a 3.5-inch downpipe and exhaust to the front of the muffler, then 4-inch pipe from the rear of the muffler to the tailpipe. The stock muffler handles the step between the two sizes. The only emissions hardware on this engine is an oxidation catalytic converter, and the parts on this page are for the cat-back section, behind it, where the converter stays in place.

Why owners change it

That 3.5-inch section is a restriction. On trucks with even mild upgrades, or on trucks towing heavy loads, it raises drive pressure and exhaust temperature. You see it as high EGT on grades and slow spool. The compliant fix is a 4-inch or 5-inch cat-back system, and it takes the right pipe and fittings to put one together cleanly.

What we carry

This is a small, practical part of our exhaust lineup:

• MBRP universal pipe and adapter: a universal pipe section and a universal exhaust adapter for joining sections when you build or repair a system.
• Banks Power 53799 pipe kit: a 36-inch section for Banks exhaust systems, listed for 1998.5-2007 Cummins.

For sound control, the MBRP mufflers and resonators for this truck, including Quiet Tone models, are in the Mufflers collection, and tips are under Accessories.

Planning a cat-back build

Start with what is on the truck now. Check whether it still has the stock 4-inch section behind the muffler, measure the pipe wherever you plan to join, and decide on 4-inch or 5-inch for the new system. Aftermarket 4-inch systems use a straight-through muffler or a resonator where the stock muffler was, and the exact layout varies from one brand's kit to the next. Read the product page for diameter and length before you order.

Fitment notes

For the Dodge Ram 2500 and 3500 only, never the Ram 1500. Cab and bed length decide the tailpipe section, and MBRP lists 2003 and 2004 trucks under separate fitments, so verify by wheelbase. Exhaust part numbers split at 2004.5 when the turbo and downpipe changed, so check each listing for 2003-2004 fitment. Use the fitment checker or call the shop in Wildwood, FL.

Frequently asked questions

Are these complete exhaust systems?

No. These are pipe sections and fittings for building or repairing the cat-back part of the exhaust. They help when you are joining a new system to existing pipe or changing one section, and they go behind the oxidation catalytic converter, which stays on the truck.

What size pipe does a 2003-2004 Ram 5.9L Cummins use?

From the factory it runs 3.5-inch from the turbo to the front of the muffler and 4-inch from the rear of the muffler to the tailpipe. If the exhaust has been changed by a previous owner, measure before you buy.

Can I go to 5-inch on a 2003-2004?

Yes. The compliant upgrades for these trucks are 4-inch or 5-inch cat-back systems, and either one moves past the restrictive 3.5-inch stock section. Because cab and bed length change the tailpipe section, verify by wheelbase before ordering.

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.