YUANTUO Trailer Axle Oil Bath Dust Caps 3.5" OD 12-Thread Clear Polycarbonate – 4 PCS with O-Rings & Plugs

YUANTUO K71-704-00 21-88 oil bath dust caps are transparent polycarbonate axle seals designed to keep lubricant in and contaminants out for compatible Dexter trailer drum assemblies.

This 4-piece kit supplies replacement oil bath dust caps and installation accessories sized for 3.5" thread OD with 12 threads, matching Dexter drum numbers listed for post-2009 and post-2013 production. Each cap is made from clear, durable polycarbonate so you can inspect lubricant level and condition without removing the cap. The set includes spare rubber plugs and O-rings so you can install the caps right away and restore reliable sealing for your axle hubs.

How do these dust caps protect my trailer axle?

The dust caps form a tight barrier at the axle hub to retain lubricating oil and block dirt, water, and road debris from reaching bearings and seals. Because they are made from a tough, transparent material, you can monitor the seal area visually and detect leaks or contamination early.

• Keeps oil inside the axle assembly where bearings ride in proper lubrication.
• Prevents ingress of water, grit, and salt that accelerate wear and corrosion.
• Clear material allows quick visual inspection without disassembly.
• Includes O-rings and rubber plugs to ensure a proper fit and immediate installation.

Will these caps fit my Dexter drums and axle sizes?

These caps are specified as model K71-704-00 with a 3.5" thread outer diameter and 12 threads; they are compatible with Dexter Drum Number 8-415 (after July 2009) and Drum Number 8-430 (after April 2013). Verify your drum part number and thread dimensions before ordering to ensure a correct fit.

• Model: K71-704-00, also labeled 21-88 in kit listings.
• Thread OD: 3.5 inches, 12-thread design for matching hubs.
• Compatible drums: 8-415 (post July 2009) and 8-430 (post April 2013).
• Includes matching rubber plugs and O-rings for secure installation.

How simple is installation and what comes in the box?

Installation is straightforward: remove the old dust cap, inspect bearing condition, fit the new cap, and seat the included O-ring or plug as needed. The kit arrives ready-to-install so you can complete the replacement during routine maintenance or as a quick field fix.

• Kit contents: 4 oil caps, 4 rubber plugs, 4 O-rings — everything needed for four hubs.
• Material is durable polycarbonate for impact and weather resistance.
• Transparent finish enables quick checks of lubricant presence and cleanliness.
• Designed for direct fit on compatible Dexter drum numbers—no custom machining.

When should I replace these dust caps?

Replace caps whenever sealing weakens, the cap shows visible damage, the material becomes deformed, or during scheduled service intervals. Regular replacement and inspection help maintain axle lubrication and prolong bearing life.

• Replace if cap has cracks, deep scratches, or visible deformation.
• Swap during routine brake or hub service to ensure fresh seals.
• Change if lubricant leakage or contamination is detected behind the cap.
• Using the supplied O-rings ensures a proper seal after replacement.

Who is this for: This YUANTUO K71-704-00 kit is intended for trailer owners, fleet maintenance technicians, and DIY mechanics who maintain Dexter 9K/10K axle hubs using Drum Numbers 8-415 (after July 2009) or 8-430 (after April 2013). It suits anyone who needs a reliable, visible oil-bath seal with quick installation and a complete set of replacement accessories for up to four hubs. Always confirm drum number and thread dimensions before purchase to ensure compatibility.