4-Inch or 5-Inch? Making Sense of Pro Power Diesel Exhaust Systems
You've decided your truck needs an exhaust. Good. Then you open the category page and it's a wall of options — 4 inch, 5 inch, race pipe, full system, with muffler, without muffler, cab and chassis, polished, rear section only. Twelve listings that all sound like the same thing.
They're not the same thing. Here's how the Pro Power Diesel lineup actually breaks down, and how to pick the one that fits what you're doing.
Everything Here Is T304 Stainless
Start with what doesn't vary. Every pipe Pro Power Diesel builds is T304 stainless steel — not aluminized, not T409.
That distinction matters more than most people realize. Aluminized exhaust is mild steel with a thin aluminum-silicon coating. It's cheap and it works until the coating gets nicked, and then it rusts from the inside out. T409 is a true stainless but a low-chrome one that surface-rusts and goes orange within a couple of winters. T304 has roughly 18% chromium and 8% nickel. It holds up to road salt, it doesn't scale, and it looks the same in year five as it did in year one.
If you live where they salt the roads, this is the whole ballgame. You're not paying for a louder truck. You're paying to do this once.
The Four Product Types
Race Pipes
The shortest piece in the catalog and usually the cheapest entry point. A race pipe replaces the factory aftertreatment section — the stretch of pipe between the turbo and the tailpipe where all the emissions hardware lives. It's a single straight section.
These are the ones with the widest price spread, because the newer trucks are harder to build for. A 2013-2018 Cummins 4" race pipe starts at $252.49. The 2023-2026 Ford 6.7 version starts at $527.49 — more than double, because the newer Super Duty routes everything differently and needs more material and more bends.
Full Exhaust Systems
Turbo back. The race pipe section plus everything downstream, including the tailpipe and tip. This is what you want if the factory system is genuinely rotted out, or if you want the whole thing to match instead of bolting a new front section to a rusty rear one.
Available in 4 inch and 5 inch across all three platforms. Ford 6.7 spans $449.99 for the 4" up through the fully polished 2023-2026 5" system at $1,124.99.
Downpipes
The piece that bolts directly to the turbo. Sold separately because it's a common failure and wear point, and because plenty of guys build their exhaust in stages. The 2020-2026 Ford 6.7 4" downpipe is $229.99, or $329.99 for the polished T304 version. Duramax owners get the 2017-2026 downpipe at $289.99.
Rear Sections and Tips
The cheapest way to change how your truck looks and sounds without touching anything upstream. Polished 7-inch rear sections come in stock angle at $299.99 or 90-degree at $349.99. There's also a 5" last section only at $179.95 if you just cracked the back half on a rock.
4 Inch or 5 Inch?
The question everybody asks, and the honest answer is that it depends on what you're doing with the truck.
4 inch is the practical choice for a truck that tows, works, and gets driven every day. Flow is more than adequate for anything short of a serious power build, it's quieter, it tucks up better, and it costs less. On the Ford 6.7 the 4" full system starts at $449.99 against $499.99 for the 5" — not a huge gap, but the 4" is the more sensible pipe for a stock-turbo truck.
5 inch makes sense when you've actually got the power to justify it, or when you want the look. Bigger tube, deeper tone, more presence under the bed. If you're running a larger turbo or pushing real fuel, the 5" is doing something. If you're stock, it's mostly a style and sound decision — which is a perfectly fine reason, just know that's what you're buying.
The one place 5 inch clearly wins on merit is longevity in a high-EGT application. More surface area, more room, less heat soak into everything around it.
With Muffler or Without?
Nearly every system is offered both ways, usually about $100 to $150 apart. This is not a performance decision. It's a decision about whether you want to be able to hear your phone on the interstate.
Without a muffler is loud. Not "sporty" loud — loud. On a 6.7 Cummins with no muffler you'll get drone at highway cruise that most people find genuinely tiring after an hour. It's the right call for a competition truck or a dedicated toy.
With a muffler keeps the tone and kills the drone. If this is your daily driver, your tow rig, or anything you spend real seat time in, get the muffler. Nobody regrets the muffler. Plenty of people regret skipping it and end up buying one later anyway — at which point you've spent more than if you'd just ordered it that way.
Pro Power also sells the mufflers standalone in 4 inch and 5 inch, both $129.99, if you want to add one to a system you already own.
Check Your Cab Configuration
This is the one that trips people up and generates the return.
Cab and chassis trucks — the flatbed and service body chassis — route exhaust differently than a standard pickup. Different frame, different bed, different exit. A pickup system will not fit a cab and chassis truck, and vice versa.
Pro Power builds separate part numbers for it across all three platforms. If your truck came from the factory without a pickup bed, order the cab and chassis version. Ford 6.7 cab and chassis race pipes run $303.99 for 2011-2022; Cummins owners want the 2019+ cab and chassis pipe at $333.49.
Polished T304 — Worth It or Not?
The polished systems run roughly $250 to $350 over the standard T304 equivalent. Same steel, same fitment, same flow. The difference is a mirror finish instead of a mill finish.
It's honest to say this one is purely cosmetic. But it's cosmetic in a place people actually see — under a lifted truck, the exhaust is visible from the side, and a polished 5" system reads very differently than a dull one. Show trucks and clean builds are the use case. If your truck lives on a job site, save the money.
Off-Road and Competition Use
Straight talk, because it matters and because getting it wrong is expensive.
Race pipes and any system that removes factory emissions equipment are sold for off-road and closed-course competition use only. Federal law prohibits removing or disabling emissions control equipment on any vehicle operated on public roads, and enforcement against both installers and owners has gotten considerably more serious in recent years. Emissions testing requirements also vary by state and county.
Know what your local rules are and what your truck's intended use is before you order. If your truck is a registered daily driver in an area with testing, a race pipe is not the part for you — and no exhaust is worth a compliance problem.
Start Here
Rotted factory system, daily-driven Ford 6.7: the 2011-2026 4" full exhaust with muffler, from $599.49. Fits fourteen model years, quiet enough to live with, done once in T304.
Cummins owner who wants tone without the headache: the 2019+ Ram 6.7 5" full exhaust with muffler at $685.99.
Duramax, best value in the lineup: the 2020-2026 4" full exhaust at $551.99, or step up to the 5" with muffler at $761.99.
Just want to fix the ugly part: a polished 7" rear section, $299.99 stock angle or $349.99 for the 90-degree exit.
Shop the Full Lineup
We carry the complete Pro Power Diesel catalog at Urban3D — exhaust systems, race pipes, downpipes, mufflers and rear sections for the Ford 6.7 Power Stroke, Ram 6.7 Cummins, and Duramax 6.6, plus their intercooler piping, CCV kits and cold air intakes.
Shop Pro Power Diesel at Urban3D
Buy the stainless once. Get the muffler.
