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ATV City  |  SKU: 100.008
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Differential Oil Filler Cap For Honda TRX 90 250 300 350 400 420 450 500 650 680 Replacement OEM

Regular price £3.00
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A Thank You to Our Valued Customers.

This differential oil filler cap is the direct-fit replacement for the rear differential on a wide range of TRX-series quads. It restores a tight seal to keep differential oil clean and at the proper level, preventing leaks and oil contamination during trail rides or farm work. Engineered for reliable service and easy installation, it helps maintain differential longevity without the complexity of dealer parts.

Built to exacting aftermarket standards, this cap combines a durable cap body with a dependable O-ring to seal the fill port against dirt and oil leaks. It tackles common wear-and-tear issues like worn threads and degraded gaskets that lead to seepage, contamination, and oil loss. For trail or farm use, this replacement delivers consistent sealing performance and long-lasting reliability at a competitive price.

Comprehensive Vehicle Fitment

Manufacturer Models / Series Years / Details
Honda TRX 90 Various years across the TRX90 range (example notes indicate wide compatibility within the TRX family)
Honda TRX 250 Various years across the TRX 250 family
Honda TRX 300 Various years across the TRX 300 family
Honda TRX 350 Typical compatibility within the TRX 350/TRX 350-family models
Honda TRX 400 Broad TRX 400 model range years
Honda TRX 420 TRX 420 family and related variants
Honda TRX 450 TRX 450 range and equivalent variants
Honda TRX 500 TRX 500 range and equivalent variants
Honda TRX 650 TRX 650 range and related variants
Honda TRX 680 TRX 680 range and related variants

Notes: Compatibility spans multiple TRX quad models; cross-reference with OEM numbers below for exact fit. Source references indicate broad TRX compatibility for these caps.

Product Specifications

Attribute Details
OEM Reference Part Numbers 12361-300-000; 12361-035-000; 91302-001-020 (O-Ring)
Type Differential Oil Filler Cap
Manufacturer Aftermarket Replacement
Application Rear differential oil fill port for TRX-series quads
Material High-strength aluminum alloy cap with nitrile O-ring
Finish Black anodized
O-Ring Included Yes (91302-001-020), typically included in the kit
Fitment Notes Direct-fit to OEM thread geometry; compatible with listed OEM references

OEM & Aftermarket Cross-Reference Information

Part Number Brand / Type Cross-Reference Notes
12361-300-000 Honda OEM Primary rear differential cap; Interchanges with 12361-181-850 and 12361-371-980 in some listings
12361-035-000 Honda OEM Cap, tappet adjusting hole; described as applicable to ALL TRX QUAD MODELS in some retailers
91302-001-020 Honda OEM O-Ring/gasket for the cap; O-ring gasket cross-references found in related OEM catalogs
12361-181-850 Honda OEM Cross-reference Interchange note found in retailer listings
12361-371-980 Honda OEM Cross-reference Interchange note found in retailer listings
04.503 L3 Aftermarket (Valkyrie Parts) Oil Cap for Final Drive; marketed as “As 12361-300-000”

What's Included

What you get in the box:

  • Differential Oil Filler Cap
  • O-Ring (91302-001-020)

Note: Some listings may omit the O-Ring; if your kit doesn’t include the seal, order the OEM O-Ring (91302-001-020) separately.

Why Choose This Aftermarket Replacement?

  • Direct-Fit Compatibility: Precise thread and seal geometry to match the TRX rear differential fill port for straightforward installation.
  • OEM Cross-Reference: Strong compatibility with the primary Honda OEM references, reducing the risk of fitment surprises.
  • Premium Materials: Aluminum cap with a durable nitrile O-ring designed to resist oil, dirt, and solvent exposure.
  • Performance Restoration: Restores reliable sealing, preventing oil leaks and contamination that accelerate differential wear.
  • Cost-Effective Care: A fraction of OEM pricing with comparable reliability, helping you keep the quad in service longer.
  • Warranty Support: Covered by Aftermarket Replacement’s dealer-focused warranty and support network.

Installation Notes:

  • Prep the port: Clean the fill port threads and seating surface; remove any debris or paint that could affect seal seating.
  • O-ring inspection: Inspect the O-ring for cracks or deformation; replace with 91302-001-020 if there are signs of wear.
  • Lubrication: Lightly coat the O-ring with clean differential oil before installation to aid seating and prevent pinching.
  • Thread engagement: Start by hand to avoid cross-threading; once snug, use a torque that feels firm but not over-tightened (no specified torque in this listing).
  • Leak check: After installation, run the engine and inspect the diff area for leaks; top off diff oil to the correct level if needed.
  • Post-install inspection: Recheck after a short drive; re-torque if necessary and ensure the O-ring remains seated and undamaged.

Why Upgrade?

Running a worn or damaged differential filler cap invites oil leaks and dirt ingress, compromising lubrication and accelerating differential wear. This aftermarket replacement restores a robust seal and proper fill-port protection, preserving differential reliability and extending the life of the rear drivetrain.

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