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Trailer Air Spring 9978, 9in Top Plate

Rolling lobe trailer air spring (9978 style) with 9 inch top plate. Replaces cracked or leaking bags on Hendrickson trailer suspensions; inspect shocks at replacement.

  • 4.5-5.0mm Thick Rubber: Heavy-duty rubber bellows for long service life.
  • 4140-Grade Steel Studs: High-tensile 4140-grade steel mounting studs, 25% stronger than standard.
  • Reinforced Composite Piston: Durable 8.05" composite piston for stable ride height.
  • Fitment
  • OEM Reference
  • Condition
  • Warranty
  • Brand
Wholesale pricing for approved accounts

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Terms and Conditions
30-day money-back guarantee
Shipping: 2-3 Business Days

Internal Reference: FP-01-9978C

  • Same-day shipping before 12PM CT from our Illinois warehouse
  • Part requests and quotes answered within one business hour
  • 30-day returns
  • 1-Year FleetPro Warranty
  • Wholesale and fleet pricing for approved business accounts
  • We speak English, Russian, Ukrainian, Romanian, Bulgarian, French and Polish

Restore your commercial suspension's load-carrying capacity with this premium Heavy Duty Trailer Air Spring by FleetPro Parts & Tires. Engineered as a direct aftermarket replacement rolling lobe/reversible sleeve air spring, this unit provides superior load support, vibration dampening, and long service life. Whether you are hauling heavy freight across the Midwest or navigating rough construction sites, this air spring ensures your trailer remains level, protecting both your cargo and your chassis. We stock these heavily right here in our Hanover Park, Illinois warehouse to ensure lightning-fast shipping for fleets and owner-operators nationwide.

Commercial Load Support: The Heavy Duty Trailer Air Spring Advantage

This Heavy Duty Trailer Air Spring is overbuilt to survive the demanding environments of long-haul trucking. It features a premium 4.5-5.00 mm thick rubber construction that exceeds standard OEM requirements, heavily resisting dry rot, ozone cracking, and road debris. Furthermore, it is equipped with 4140-grade steel studs that are 25% stronger than standard hardware, preventing sheer failures under extreme articulation. Paired with a reinforced composite piston and an industry-leading leak test ratio, this aftermarket air spring delivers reliable, airtight performance shift after shift.

As we continue to grow the largest inventory of commercial truck parts in Illinois, we prioritize suspension hardware that balances industrial strength with cost-effective reliability. Serving as a direct exact-fit replacement for massive industry part numbers including Firestone W01-358-9978, Hendrickson S28929, and Goodyear 1R12-668, this unit is ready to bolt right on and save you from dealership markups. Important Fitment Note: Buying an air spring by make and model alone is not recommended. Always verify your replacement by crossing your original part number or measuring your top/bottom plate mounting configurations prior to purchase.


Vehicle Fitment & Compatibility

This premium aftermarket trailer air spring features a universal design intended for the following commercial applications:

  • Make: Universal Trailer Fit (Hendrickson, Freightliner, Volvo, Mack, Alliance, etc.)
  • Application: Trailer Air Suspension Systems
  • Suspension Type: Rolling Lobe / Reversible Sleeve

Direct Replacement & Cross-Reference Numbers:

This air spring serves as a direct exact-fit replacement for the following part numbers:

  • Firestone: W01-358-9978, W01-358-6262, W01-358-6231, 9978, 99978, 6262, 6231
  • Hendrickson: S28929, S-28929, C28929, HENS-28929
  • Goodyear: 1R12-668, 1R12-1179, GYR1R12668, GYR-1R12-668, 8235FS9978
  • Continental / ContiTech: 910-14P959, 910-17.5P831, 67588, 77303
  • Automann: 566.CT67588, AB1DK23I-A959, AB1DK23I-P959, AB1DK23P-6262
  • Meritor: FS9978, FS6262, FS6231
  • Other Aftermarket: TR9978 (Torque), AS-9978 (Triangle), 352-9978 / 452-9978L (Dayton), N32 559978 (Alliance), S28501 (Newstar)

Technical Specifications
  • Top Plate Diameter: 9.00"
  • Top Plate Hardware: 2 Bolt Holes (5.5" Center-to-Center)
  • Bottom Plate Diameter: 10.24"
  • Bottom Plate Hardware: 1 Bolt Hole (2.25" Center-to-Center)
  • Extended Length: Approx. 19.6" - 22.00"
  • Compressed Length: Approx. 7.8" - 8.20"
  • Piston Width: 8.05"
  • Warranty: 3-Year Unlimited Mile
  • Brand: FleetPro Parts & Tires

Cross references: 1R12-668 • S28929 • Firestone W01-358-9978 • Hendrickson C-28920 • Meritor FS9978

Specifications

Fitment Hendrickson trailer suspensions (9978)
OEM Reference Meritor FS9978
Condition New
Warranty 1-Year FleetPro Warranty
Brand FleetPro