Frequently Asked Questions About Freightliner FLC120 DPF & Mufflers

Will these DPF and muffler systems fit my specific year FLC120?

Most aftermarket DPF and muffler systems for the FLC120 are designed to fit models from 1990-2003. However, there are variations based on engine type (Caterpillar, Cummins, or Detroit Diesel) and whether your truck has a standard or extended hood. Always verify your engine model and year before ordering. Systems for pre-2007 trucks typically don't include DPF units since these weren't required until EPA 2007 regulations.

What's the difference between aluminized steel and stainless steel mufflers for my FLC120?

Aluminized steel mufflers typically last 3-5 years and cost 30-40% less than stainless options. They're adequate for moderate climates and standard hauling. Stainless steel mufflers can last 7-10 years or more and resist corrosion better in harsh conditions, salt exposure, or frequent washing. For FLC120s operating in northern states or coastal areas, the extra investment in stainless steel often pays off through extended service life.

Can I install these muffler systems myself, or do I need a shop?

Basic muffler replacement on an FLC120 can be done with standard tools including jack stands, wrenches, and exhaust hangers. Most straight-through replacements take 2-3 hours for experienced DIYers. However, if you're installing a complete DPF system or modifying pipe routing, professional installation is recommended due to alignment requirements and potential ECM programming needs. Always ensure proper clearance from air lines, fuel tanks, and cross members.

How do I know if I need a straight-through or chambered muffler design?

Straight-through mufflers provide maximum flow and minimal back pressure, ideal for high-performance applications or engines with turbo modifications. They're typically louder with a deep rumble. Chambered mufflers reduce noise levels by 3-5 dB and meet most state noise regulations while maintaining good flow characteristics. For FLC120s used in urban delivery or noise-restricted areas, chambered designs are usually the better choice.

What size exhaust pipes and mufflers do I need for my FLC120?

Standard FLC120s typically use 5-inch diameter exhaust systems, though some high-horsepower variants may have 6-inch systems. Muffler body sizes usually range from 10" to 12" in diameter and 30" to 44" in length, depending on available frame space. Measure your existing system carefully, noting inlet/outlet positions (center/center or offset) and overall length constraints. Stack-exit models require different configurations than side-exit systems.