Air Spring W01-358-9781

Firestone air bag for highway tractors

Firestone air springs appear on steer, drive, and tag axles where rubber bellows replace steel leaf stacks. The W01-358-9781 style bag on this listing replaces a failed unit when ride height collapses or sidewall cracks appear at the convolutions.

Air system health matters as much as the bag itself. A leaking leveling valve or blocked supply line mimics spring failure. Confirm pressure and valve travel before you condemn the rubber.

This page sells the air spring described in the product title. Mounting plates and shock absorbers remain inspection items on the same axle job.

Fitment table orientation

Examples include Freightliner, Kenworth, Peterbilt, and Volvo tractors with All engine rows. Verify bead plate geometry and port location against the removed spring using photos and VIN data when available.

Use the fitment guide to compare adjacent Firestone listings when multiple W01 numbers appear in fleet history.

Questions go to support@aonetruckauto.com with axle tag photos attached.

Card weight and price

Published ship weight is 14.5 lb. Price is $179.00 USD before tax.

Carrier rules and return windows are on the shipping policy and returns and refunds pages.

Port and bellows verification after install

Inflate gradually and watch the bellows unfold evenly. A twisted install shows as uneven convolution spacing before the truck leaves the bay.

Spray-check the air port and bead gasket at operating pressure. Residual leaks pull compressors into continuous duty and ice the dryer in winter.

Suspension PM pairing

• Inspect shock mounts when the bag is deflated; worn bushings shorten new bag life.
• Confirm bump stops are present and correct height before loading.
• Reset height control linkage if the axle was jacked during service.
• Record corrected ride height in the fleet maintenance portal.

Photograph the old spring stamp before scrap pickup so purchasing can reconcile invoices.

Receiving

Inspect carton crush damage; sharp bends stress bead wires inside the pack. Report damage before install if carrier claims apply.

Steer versus drive air spring differences

Steer axles see lateral load from road crown and braking dive that drive axles feel differently. The same part book family may list multiple bellows heights for that reason. Photograph both sides when only one corner collapsed.

Shock valving mismatched to air spring rate produces harsh ride that drivers report as failed bags. Pair shock inspection with every bag swap on the same corner.

Alignment should be checked when steer height changes more than a fleet tolerance band after spring service.

Yard obstacles to avoid

• Do not weld near installed bags; heat damages rubber compounds.
• Keep fork lifts from lifting by bellows instead of approved lift points.
• Deflate bags before removing U-bolts on some walking beam designs.
• Route air lines away from sharp frame edges after reinstall.

Mechanical damage during install negates careful stamp matching on the purchase order.

Firestone numbering in mixed inventories

Warehouse bins sometimes mix adjacent W01 numbers with similar cartons. Scan labels at pick time and compare to the purchase order line before the tech leaves the parts window.

Air spring failures after long storage indoors still happen when cartons sat under leaking roof panels. Feel for stiff bellows that crack on first inflation.

Leveling system fault codes

Some chassis display height fault codes when air springs fail or when sensors detach. Clear codes only after mechanical repair and a calibrated height check, not before confirming ports seal at operating pressure.

Drivers report leaning cabs after fuel load shifts; verify height on level ground with tanks full when complaints follow recent bag work.

Firestone bag inflation tooling

Use regulated shop air through inline water separators when inflating bags on the bench; moisture in shop lines contaminates bead paths before the unit ever sees road miles.

Compare port orientation to photos taken before removal; mirrored installs leak at the first loaded corner.

Trailer bag parity

When tractors sit high on new drive bags but trailers ride low, check trailer bags separately; drivers report combo lean that is not solved by tractor suspension alone.

Firestone bags paired with steel leaf auxiliary springs need height valve recalibration when leaf packs are removed during suspension conversions; verify port seals after those larger projects complete.

Document bellows serial tags when your fleet tracks air spring life by months in service; photos beat memory when units swap between regional pools.

Rolling-lobe clearance through dump cycles

Firestone rolling-lobe bags need a clear path when the axle dumps. After install, cycle ride height from full lift to dump while watching for rub on heat shields and brake chambers.

Bead plate bolts that stretch after winter salt often look fine until the bag leans under load. Replace stretched hardware rather than over-torquing corroded studs.

Trailer and tractor bags can share family numbers with different heights. Measure plate-to-plate height on the removed unit before you assume this listing matches a trailer position.

Soap-check the air stud after the first loaded trip. Slow leaks at the stud show up as a low corner on the scale, not as a loud hiss in the yard.

Winter salt and bead hardware

Salt season stretches bead plate bolts on Firestone bags. Inspect hardware when you replace the bellow and renew stretched studs instead of chasing torque on rounded heads.

Mark ride height valve positions before you disconnect linkages so the new bag settles to the same corner heights the driver expects.

Packaging and carrier options are described on the shipping policy. Return eligibility is on returns and refunds. Questions: support@aonetruckauto.com.

HEAVY TRUCK PARTS, INC. operates A-One Truck Auto. Truck and brand names here describe compatibility only; we are an independent seller.