What This Air Spring Does
The 1S6-026 is a cab and sleeper mount air spring, not a chassis or drive axle bag. It sits between the cab mount bracket and the frame and carries a small share of the cab weight while the air suspension controls ride height. It is a sleeve design: a rolling flexmember over a piston, no bellows convolutions.
The assembly is light, roughly 1.75 lb, which tells you it is a cushioning component rather than a load-bearing suspension bag. That low mass is also why techs sometimes mis-order a larger chassis bag when the tag is gone. Position matters here more than diameter alone, so confirm you are working on the cab mount.
Failure is usually straightforward. The sleeve chafes or cracks at the rolling lobe, the bag loses air overnight, and the cab drops onto its stops. You get a hard ride, door alignment complaints, and often a whistle from the leveling valve line while the compressor cycles more than it should.
Why These Numbers Cross
227QS310BM, 227QS310AM and 227QS310M are the Mack service numbers for the same 227QS310-series cab air suspension bag, with the suffix marking supersession rather than a different part envelope. 8633-1S6026 and 7843-1S6026 are the same base 1S6-026 sleeve carried under different Mack packaging prefixes.
804262 is the PAI number for the same cab air spring, and AS2-08-5-048 is the Stemco listing. All of them describe a sleeve flexmember of the same bore, stroke and mounting pattern, which is why they land on one line in the interchange. The headline 1S6-026 is the flexmember designation itself, so it shows up across several catalogs unchanged.
These numbers are listed for identification only. PartStop is not affiliated with, endorsed by, or authorised by Mack, PAI, Stemco or any other manufacturer. A cross-reference is a starting point — confirm fit by VIN or by reading the number cast or printed on the bag you are removing.
Check Before You Order
Pull the old bag and read it. Cab air springs on older Mack conventional and cabover trucks were revised over the production run, and the printed number on the flexmember is the fastest confirmation you have. If the print is gone, measure the mounted height and the stud or port spacing before committing.
Look at what killed the first one. A leaking bag that only lasted a short time usually points at a bracket rubbing the sleeve, a collapsed bump stop, or a leveling valve holding the cab too high. Replace the bag and leave the cause in place and you will be back under the cab soon.
1S6-026 Cross-Reference & Interchange Numbers
These manufacturer and aftermarket numbers commonly cross-reference to 1S6-026. 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 |
|---|---|
| Mack | 227QS310BM, 227QS310AM, 227QS310M, 8633-1S6026, 7843-1S6026 |
| PAI | 804262 |
| Stemco | AS2-08-5-048 |
Frequently asked questions
Is 1S6-026 the same as Mack 227QS310BM?
They cross to the same cab suspension air spring. 227QS310BM is the Mack service number and 1S6-026 is the sleeve flexmember designation. 227QS310AM and 227QS310M are earlier revisions of the same Mack part. Confirm by the number on your old bag or by VIN before ordering.
How do I know if my cab air spring is leaking or the leveling valve is bad?
Air the system up, shut the truck down, and spray the bag and fittings with soapy water. Bubbles at the rolling lobe or a split in the sleeve mean the bag is done. If the bag holds and the cab still sags or rides high, the leveling valve or its linkage is the suspect.
Will this fit my Mack if the old part number is 804262 or AS2-08-5-048?
Those are the PAI and Stemco numbers for the same cab air spring and appear on the same interchange line. We list them for identification only. Cross-reference is a starting point, not a fitment promise — verify your cab suspension model, mounting and ride height before you order.
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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