National Wheel Seal 370003A for Isuzu & GM Medium-Duty Trucks — Oil-Bath, Nitrile Spring-Loaded

National 370003A is a heavy-duty wheel oil-bath seal engineered to stop axle leaks and protect wheel bearings on select Isuzu and GM medium-duty trucks.

Built by National, a long-established name in sealing technology, this wheel seal combines a reinforced unitized body, abrasion-resistant nitrile, and a spring-loaded lip to deliver reliable sealing performance across a wide temperature range. It’s designed for vehicles that originally used oil-bath axle arrangements and for technicians who need a robust replacement that resists shaft wear and bore damage.

Which vehicles does this wheel seal fit?

The 370003A fits a range of Isuzu and Chevrolet/GMC medium-duty truck models across late-1990s and 2000s production years. Fitment covers FTR, FVR, HTR, HVR Isuzu models and several Chevrolet Kodiak/T series and GMC TopKick variants—always confirm exact year, model, engine and trim before ordering.

• 1995–2011 Isuzu FTR series compatibility
• 1995–2004 Isuzu FVR and 2005–2008 Isuzu HTR/HVR coverage
• 1997–2009 Chevrolet C6500/C7500 Kodiak and T6500/T7500 models
• 2003–2009 GMC C6500 TopKick inclusion

How does the 370003A seal prevent leaks and shaft damage?

This seal uses a spring-loaded main sealing lip paired with abrasion-protected nitrile to maintain contact pressure while minimizing interference with rotating shafts. A molded inner and outer rubber surface includes patented SURE-LOCK ribs to lock the seal in the bore and reduce leak paths around the ID/OD.

• Spring-loaded lip for consistent pressure and oil retention
• Abrasion-resistant nitrile reduces wear from shaft contact
• SURE-LOCK ribs secure the seal to the bore and inhibit seepage
• Unitized construction protects the main lip and simplifies installation

What operating conditions can this wheel seal handle?

Designed for heavy-duty vehicle environments, the 370003A functions across sub-freezing to hot under-hood temperatures, maintaining elastomer flexibility and lip integrity. Its materials suit oil-bath applications where continuous lubricant contact and moderate thermal cycling occur.

• Temperature range: approximately -40°F to 225°F (-40°C to 107°C)
• Oil-bath optimized design for continuous lubrication systems
• Durable unitized structure for improved service life under load

What should a technician check before installing this part?

Confirm exact vehicle fitment using the vehicle lookup or fitment notes, inspect axle shaft and bore for scoring, and replace or recondition mating surfaces as needed. Proper installation and clean bore surfaces are critical to reach the intended sealing life.

• Use vehicle year/make/model/engine/trim to verify fit
• Examine shafts and bores for wear; replace if deeply scored
• Follow installation guidance to avoid lip damage and ensure bore seating

Who is this for: The National 370003A is aimed at commercial fleet mechanics, independent truck service shops, and owners of medium-duty Isuzu and GM trucks who need a dependable oil-bath wheel seal replacement. It’s suited to professionals seeking a unitized, heavy-duty seal that resists abrasion, locks securely in the bore, and tolerates the rigors of daily heavy vehicle operation.