The Rear Diff Complete for Honda TRX420FA, TRX500FA, and TRX520FA IRS models is a purpose-built aftermarket replacement that restores precise final-drive function and smooth power transfer from the engine to the wheels. Designed to fit 2015–2025 TRX420FA IRS, 2015–2019 TRX500FA IRS, and 2020–2025 TRX520FA IRS machines, this complete rear differential assembly brings you factory-like engagement and reliability without the OEM price. Built to endure off-road conditions, it eliminates the driveline lash, grinding, and oil leaks that plague a worn rear gearcase, so you can stay confident on trails or work sites.

This aftermarket replacement delivers a reliable, maintainable solution for riders who demand consistent performance in rugged environments. Its design emphasizes accurate alignment with OEM mounting points and durable components to resist the punishment of trail riding and farm use, ensuring long service life and predictable operation when you need it most.

Comprehensive Vehicle Fitment

Product Specifications

OEM & Aftermarket Cross-Reference Information

What's Included

The box includes the complete Rear Diff Assembly ready for installation.

• Rear Diff Complete Assembly

Why Choose This Aftermarket Replacement?

• Direct-Fit Compatibility: Precisely matched mounting points and connectors to preserve OEM fitment and simplify installation.
• OEM Cross-Reference: Clear cross-reference to 41300-HR6-A60, 41300-HR6-660, and 41300-HR6-B00 for dependable replacement planning.
• Premium Materials: Robust steel housing and durable gear set designed for off-road protection against impacts, mud, and vibration.
• Performance Restoration: Restores correct gear engagement and driveline feel, eliminating common symptoms of a worn rear diff such as lash, noise, and loss of torque transfer.
• Reliability in Trail & Farm Use: Built for harsh environments where mud, water, and debris are common, helping prevent premature failures.
• Widespread Availability: Ready-to-order replacement with broad dealer coverage to minimize downtime.

Installation Notes:

• Secure the ATV on a level surface and support the frame with jack stands before working on the rear diff.
• Drain the differential oil before removing the old unit to reduce drips and spills.
• Inspect and replace seals, gaskets, and mounting hardware as part of the install to ensure a leak-free fit.
• Clean mating surfaces and verify the OEM mounting points align with the new assembly prior to bolt-up.
• Install with the vehicle in a level position to maintain proper differential fluid level and prevent overfilling.
• Refill with the OEM-recommended gear oil to the proper level after installation and perform a short, low-load test before returning to full duty.

Why Upgrade?

Running a worn or damaged rear differential on these IRS Hondas can lead to uneven power delivery, increased driveline lash, and unexpected failings under load—especially when riding demanding trails or performing farm tasks. Upgrading to this aftermarket Rear Diff Complete restores reliable torque transfer, reduces noise, and reestablishes predictable operation, giving you confidence from the first ride after service.