What This Bellows Actually Is
This is a flex section, not a straight pipe - it's a corrugated stainless bellows welded between two pipe ends, sized for the 4" to 5" exhaust runs on Cascadias built from 2008 up through the current 2024 trucks. Its whole job is to flex with engine torque and chassis twist so the rigid pipe on either side of it doesn't crack at the welds.
When these go bad you'll usually hear it before you see it - a rattling or ticking under load, sometimes a soot streak where the bellows folds have split. Freightliner used this same style flex across a long run of Cascadia exhaust configurations, straight pipe and vertical stack setups alike, which is why one number covers so many trucks and years.
Because it's a wear item that takes vibration and heat cycling every day, it's not unusual to be replacing one of these on a truck that's otherwise mid-life. Stainless construction is what gives it the runtime it has, but stainless doesn't mean it lasts forever - eventually the corrugations fatigue and crack.
How These Cross Numbers Line Up
A042857800 shows up under a few other catalog numbers - PN-3-B-037, 04-31271-001, and 03-08040002 - because different suppliers and aftermarket houses have stocked and renumbered this same bellows over the years. Same physical part, different label on the box.
The thing to actually check before you order is bellows length, the ID/OD on both ends, and overall flex diameter - 4" to 5" on this one. A bellows that's a half inch off in end diameter will either not seat in the clamp or leave you with a gap that leaks exhaust and sets off your fault codes. Don't go by year alone; two Cascadias built a year apart can carry different exhaust routing depending on engine and emissions package.
Surest way to confirm is pull the old bellows and read whatever number is stamped or tagged on it, or better yet, run your truck's VIN. That tells you exactly what left the factory on your chassis, which is worth more than guessing off a parts book.
Ordering From PartStop
We keep this bellows in stock at our Tacoma counter, so if you're local and your truck's down, you can get it same-day and be back on the road. If you're not near us, we ship it nationwide - doesn't matter if you're at a truck stop in the Midwest, it'll get to you.
This is aftermarket, not a Freightliner-branded part, and we tell every customer straight - confirm fit by VIN or by matching the number off your old bellows before you buy. We're not going to tell you it's a guaranteed fit sight unseen, because exhaust routing on these trucks isn't always as uniform as people assume.
It carries our standard 6+ month warranty. If something's off with fitment or it fails early, call the counter and we'll sort it out - no runaround.
A042857800 Cross-Reference & Interchange Numbers
These manufacturer and aftermarket numbers commonly cross-reference to A042857800. Use them to identify the part — then confirm the exact fit by VIN or the number stamped on your old unit before you order. An interchange is a starting point, not a fitment guarantee.
| Brand / Line | Cross-Reference Numbers |
|---|---|
| Cross-Reference | PN-3-B-037, 04-31271-001, 03-08040002 |
Frequently asked questions
Does A042857800 fit my 2015 Cascadia?
Likely, since this bellows spans the 2008-2024 Cascadia range, but 'likely' isn't good enough to order on. Give us your VIN or read the number off the old bellows and we'll confirm it matches before you spend $341.55 on it.
Is this the same part as 04-31271-001?
Yes, 04-31271-001 is one of the cross-reference numbers for this same bellows - different supplier catalog, same physical part. Still worth double-checking dimensions against your old unit since suppliers sometimes reuse numbers loosely.
Why does my exhaust rattle even after I replace the flex pipe?
If the rattle's still there after a new bellows, check your clamps for proper torque and make sure the pipe ends actually seated fully into the bellows collars - a loose clamp or a partial seat will still rattle and can leak exhaust even with a good part installed.
Not sure it fits? We check before you pay.
Run your VIN and we’ll match parts to your exact truck, or call the counter — a person who knows trucks verifies fitment by OEM number before the order ships. No wrong-box returns.
More cross-reference guides
Need the part, not just the reading?
Every part below is a Premium Quality aftermarket Direct Replacement with published OEM cross-reference numbers, a 6+ month warranty and same-business-day shipping from Tacoma, WA. Not sure it fits? Run your VIN — or call and a person who knows trucks will verify fitment before you pay.