What This Air Spring Is
This is a single-convolution reversible-sleeve air spring for the drive axle position. The bag rolls over a piston rather than folding like a bellows, which gives a softer rate at ride height and better control under a loaded trailer. It carries the tractor's rear corner weight and works with the height control valve to hold ride height as load changes.
Published dimensions on this bag: 23 in. extended height, 8.75 in. collapsed height, 9 in. top plate, 10.62 in. piston diameter, roughly 13.6 lb assembled. Measure your old bag before ordering. Extended height and piston diameter are the two numbers that separate similar-looking drive-axle bags on the same chassis family.
The PartStop unit is an aftermarket direct replacement, not an OEM-supplied part. We list other manufacturers' numbers for identification only. It is built for over-the-road linehaul service on Freightliner Airliner-style rear suspension and is backed by a 6+ month warranty.
Why These Numbers Cross
Air spring numbering follows the physical bag, not the truck. Firestone W01-358-9759 and W01-377-9743 are the same reversible-sleeve assembly under two part-number series — one is the base assembly number, the other a variant configuration with the same bag, plate and piston geometry. Goodyear 1R12-603 and ContiTech AS9759 (also catalogued as 9 10S-16 P 224) are those makers' equivalents built to the same envelope.
Freightliner A16-18335-000 is the chassis-side number the truck was built with. Volvo 85101151, Meritor MAF9781 and SAF-Holland G2299759200 appear because the same bag gets used across several suspension and axle packages. When multiple brands publish numbers against one envelope, it is because collapsed height, extended height, plate size and port arrangement all match.
That is the limit of a cross-reference. Matching numbers means the bag is the same shape and rate. It does not confirm the mounting studs, air port thread and piston stud on your specific chassis. Confirm by VIN or read the number stamped on the old bag before you order.
Failure Signs And Install Checks
A failed bag shows up as one rear corner sitting low, audible air leak at the sleeve or bead, or the compressor cycling more than it should. Soap the bag at ride height and again with the suspension dumped — sleeve cracks often only open when the rubber rolls over the piston. Check for chafe marks from a shifted air line or a loose shock.
Replace bags in pairs on the same axle. A new bag next to a tired one changes ride height side to side and loads the height control valve linkage. While the old bag is out, inspect the piston for corrosion and debris, check the top plate mounting surface is clean, and verify shock condition — a dead shock is a common reason a bag fails early.
W01-358-9759 Cross-Reference & Interchange Numbers
These manufacturer and aftermarket numbers commonly cross-reference to W01-358-9759. 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 | 9 10S-16 P 224, AS9759 |
| Firestone | W01-377-9743 |
| Freightliner | A16-18335-000 |
| Goodyear | 1R12-603 |
| Meritor | MAF9781 |
| SAF-Holland | G2299759200 |
| Volvo | 85101151 |
Frequently asked questions
Is W01-358-9759 the same bag as W01-377-9743?
They cross to the same reversible-sleeve drive-axle air spring envelope, listed under two Firestone number series. Same extended and collapsed heights, same plate and piston sizing. Verify the number stamped on your old bag before ordering, since fitment is confirmed on the truck, not from a catalogue line.
How do I know if it's the bag or the height control valve?
Air up the system and soap the bag and its fittings. A leaking bag will bubble at the sleeve, bead or port. If the bag holds air but the corner still sits low or hunts up and down, look at the height control valve and its linkage arm.
Do I have to replace both drive-axle bags at once?
It is the right call. An aged bag has a different spring rate than a new one, which causes side-to-side ride height differences and uneven load transfer. Doing both sides at the same time keeps the axle level and saves a second teardown when the other side lets go.
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.