What This Air Spring Is
This is a drive axle reversible-sleeve air spring. The rubber bellows rolls down over a composite plastic piston instead of folding like a convoluted bag, which gives a longer stroke and a softer rate over the road. It carries the drive axle load on Mack Anthem, Pinnacle, Granite and CHU/CXU trucks running the Hendrickson drive-axle air suspension.
Key dimensions: 22.0 in extended height, 8.1 in compressed height, 9.0 in bead plate, 10.12 in bellows outside diameter, and 6.25 in stud spacing on the top plate. Measure the stud spacing and bead plate on the old part before you order. Those two numbers separate air springs that otherwise look identical on a shelf.
Construction is multi-ply cord-reinforced rubber with a corrosion-proof piston, so the base does not rot out the way a steel piston does after a few winters of brine. This is a PartStop aftermarket part built as a direct replacement, not an OE-supplied assembly, and it carries a 6+ month warranty.
Why These Numbers Cross
Air springs get catalogued by the suspension builder, the truck OEM, and the bellows manufacturer all at once. Hendrickson designed the suspension and assigned 50899-1 and 50899-2. Mack put the same spring on the truck and called it 57QL414M. The bag itself was sourced from more than one rubber supplier over the production run, which is where Goodyear 1R12-404 and 1S12-031 come from.
ContiTech 62624, Torque TR9375 and Triangle 8451 are aftermarket catalogue numbers built to the same physical envelope: same bead plate, same stud pattern, same extended and compressed heights, same piston geometry. They all mount to the same bracket and index off the same air port location, so the suspension does not know the difference once it is inflated.
The numbers cross because the mounting interface and the load curve match, not because the parts came off the same line. That is the important distinction. A cross-reference tells you the part will bolt where the old one bolted and hold the same ride height — it does not replace checking your VIN or reading the tag on the spring you are pulling off.
Failure Signs And Install Checks
The usual failure is a pinhole or a sidewall crack at the rolling lobe, where the bellows flexes over the piston every mile. You get slow overnight leak-down, one corner sitting low, and the compressor cycling more than it should. Soap the bag with the system aired up and watch the lobe area and the bead plate seal. A dry-rotted bag that is weather-checked all over is going to fail soon even if it holds air today.
Replace in pairs across the axle. A new spring next to a tired one shifts load and chews up the new one. Support the frame, dump the air, and check the height control valve linkage while you are in there — a bag that failed early often had a valve holding it over-inflated. Torque the bead plate studs evenly and check ride height against spec after the system charges.
W01-358-9375 Cross-Reference & Interchange Numbers
These manufacturer and aftermarket numbers commonly cross-reference to W01-358-9375. 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 |
|---|---|
| ContiTech | 62624 |
| Goodyear | 1R12-404, 1S12-031 |
| Hendrickson | 50899-1, 50899-2 |
| Mack | 57QL414M |
| Torque | TR9375 |
| Triangle | 8451 |
Frequently asked questions
Will this fit my Mack if the old bag has no readable number?
Measure before you order. You need 9.0 in bead plate diameter, 6.25 in stud spacing, and roughly 10.12 in bellows diameter with a 22.0 in extended height. If those match, you are in the right family. Confirm by VIN or by the number on the removed part before you commit — cross-reference is a starting point, not a fitment guarantee.
What is the difference between Hendrickson 50899-1 and 50899-2?
Both are Hendrickson catalogue numbers for the same drive axle spring position and both cross to W01-358-9375. Suffix changes on air spring numbers typically reflect a running production revision or an alternate bellows supplier rather than a change in mounting or height. Check the number on your old part and match dimensions to be sure.
Do I have to replace both drive axle air springs at once?
Replace them in pairs across the axle. An aged bag has a different spring rate than a new one, so the new spring takes more of the load and works harder. You will also want to inspect the height control valve and linkage, since a misadjusted valve can over-inflate a bag and cut its life short.
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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.