What This Air Spring Is
This is a rolling-lobe, reversible-sleeve air spring for the drive axle position. The rubber sleeve rolls over a composite piston as the axle moves, instead of folding like a convoluted bag. That design gives a flatter spring rate through travel, which is why it shows up under loaded line-haul and severe-service chassis rather than on trailer or cab suspensions.
Key dimensions: roughly 22 inches extended, roughly 5.9 inches compressed, 9 inch steel bead plate on top, 10 inch piston at the bottom, single air connection through the top plate. Measure your old bag before ordering. Air spring part numbers change with plate diameter and piston diameter more often than with anything else on the unit.
The PartStop unit is an aftermarket direct replacement, not a factory part. Steel bead plate top, composite piston bottom, built to the same ride height and load range as the original. It carries a 6+ month warranty. We are not affiliated with, endorsed by, or authorised by any OEM listed here.
Why These Numbers Cross
W01-358-9648 is the Firestone catalog number. Navistar bought that same bag and assigned it OE number 2027911C1 for chassis production and dealer parts. Goodyear built a functionally identical spring as 1R12-398, ContiTech catalogs it as 73770 with engineering designation 9 10S-16 P 1068, and Triangle sells it as 8456. Same bellows, same plate, same piston, different label.
The remaining numbers are distributor and reseller listings. Meritor lists FS9648, Dayton Parts uses 352-9648, and Automann catalogs AB1DK23M9648. Notice the trailing 9648 repeating through several of those. That is not coincidence — resellers commonly carry the Firestone suffix forward so counter staff can match numbers fast without a full interchange lookup.
All of these numbers describe an air spring with the same extended and compressed height, the same 9 inch top plate, the same 10 inch piston, and a single top air port. That combination is what makes them interchangeable. These numbers are listed here for identification only and are the property of their respective manufacturers.
How These Fail And What To Check
Reversible-sleeve bags usually fail one of three ways. The sleeve chafes through where it rolls against a bent or corroded piston. The bead plate crimp corrodes and weeps at the top. Or the bag gets run flat, folds against the piston edge, and cuts itself. Soap-and-water the whole unit at ride height and again at full droop — a lot of leaks only open under one condition.
Before you order, confirm the number on the old part or verify by VIN. Cross-reference is a starting point, not a fitment promise. Check the piston for rust scale and the mounting studs for stretched or pulled threads, and inspect the height control valve linkage while you have the wheel off. A worn valve will kill a new bag the same way it killed the old one.
W01-358-9648 Cross-Reference & Interchange Numbers
These manufacturer and aftermarket numbers commonly cross-reference to W01-358-9648. 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 | AB1DK23M9648 |
| ContiTech | 73770, 9 10S-16 P 1068 |
| Dayton Parts | 352-9648 |
| Goodyear | 1R12-398 |
| Meritor | FS9648 |
| Navistar | 2027911C1 |
| Triangle | 8456 |
Frequently asked questions
Do I have to replace both drive axle air springs at once?
Not required, but it is normal shop practice. A new bag next to an old one with cured, hardened rubber will sit and ride slightly differently side to side. If the truck has high mileage and one bag failed from age rather than impact damage, the other side is usually not far behind.
Is 1R12-398 the same air spring as W01-358-9648?
Yes, they cross to the same physical part. 1R12-398 is the Goodyear number and W01-358-9648 is the Firestone number for a reversible-sleeve drive axle spring with a 9 inch top plate and 10 inch piston. Confirm the number on the bag you pulled off, or verify by VIN, before you order.
Why does my new air spring sit at the wrong ride height?
Almost always the height control valve, not the bag. The valve linkage arm gets bent during service or the valve itself sticks after years of road grime. Set ride height to the chassis specification with the arm disconnected, then reconnect and confirm the valve exhausts and fills cleanly.
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.