What This Air Spring Is
This is a single-convolution rolling-lobe air spring, also called a reversible sleeve bag. The bellows rolls down over a composite piston instead of folding like a convoluted bag. Design height is roughly 13.23 in, piston diameter about 10.62 in, and the top plate measures 9 in. Air inlet is M12x1.5 and the mounting stud is 1/2-13 UNC.
It sits on the drive-axle position of the Freightliner AirLiner rear suspension. The bag carries the load, the shock controls the motion, and the height control valve meters air in and out. If any one of those three is wrong, the bag takes the abuse and fails early.
Sold each. Replace them in pairs across the axle, or as a full set on a tandem. A new bag beside a five-year-old bag gives you uneven ride height, uneven load transfer, and a leaning trailer deck.
Why These Numbers Cross
Freightliner does not build the bag. It specs a bellows and piston assembly from a supplier and assigns its own number, A16-21554-001. The same assembly carries the supplier's own part number, which is why one physical air spring shows up under half a dozen catalog listings.
Firestone W01-358-9780 and W01-377-8400 use the 1T15ZR-6 bellows on the same piston; W01-358-9759 is the same family. Goodyear 1R12-303, ContiTech 9 10S-16 P 382, Triangle AS-8382P, Automann 1DF23-9780, and Volvo 85101151 all describe the same rolling-lobe geometry — same design height, same piston diameter, same top plate, same M12x1.5 inlet and 1/2-13 stud.
Those numbers are listed here for identification only. PartStop is not affiliated with, endorsed by, or authorized by any of those manufacturers. The cross is a starting point for finding the right bag, not a guarantee it fits your chassis.
Check Before You Order
Read the old bag. The number is usually printed or stamped on the top plate or molded into the bellows near the crimp. If it is legible, that number beats any catalog lookup. If the bag is shredded, pull the piston and check the stud and inlet thread sizes against the specs above.
Measure design height with the truck at normal ride height and loaded the way it normally runs. Then confirm the height control valve is holding. A bag that keeps blowing out at the top of the rolling lobe usually means the valve is dumping late or a shock is dead and letting the axle top out.
Verify fitment by VIN or by the number on the part you removed. Freightliner used more than one suspension configuration across Cascadia, Columbia, and Century Class, and the cross-reference alone does not confirm fit on your specific truck.
A16-21554-001 Cross-Reference & Interchange Numbers
These manufacturer and aftermarket numbers commonly cross-reference to A16-21554-001. 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 |
|---|---|
| Automann | 1DF23-9780 |
| ContiTech | 9 10S-16 P 382 |
| Firestone | W01-358-9780, W01-377-8400, W01-358-9759 |
| Goodyear | 1R12-303 |
| Triangle | AS-8382P |
| Volvo | 85101151 |
Frequently asked questions
How do I know if the air bag is leaking or the height control valve is bad?
Air the system up, shut the truck down, and spray soapy water on the bellows, the top plate crimp, and the piston seal. A leak at the crimp or a split in the bellows means the bag. If the bag is dry and the suspension still drops overnight, look at the height control valve and its exhaust port.
Do I have to replace both air springs on the axle?
You should. The bag is sold each, but a new bag next to a worn one sits at a slightly different height and carries a different share of the load. That shows up as a leaning frame and uneven tire wear. Do them in pairs across the axle, or all four on a tandem.
Will this bag fit my Cascadia if the old part number is unreadable?
Maybe, but confirm it first. Measure the design height, piston diameter, and top plate, and check the air inlet and mounting stud threads against the specs listed. Then verify by VIN. The cross-reference list identifies the same assembly under other brand numbers; it does not promise fitment on your chassis.
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
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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.