Rear Diff Complete for Honda TRX300 Fourtrax / Big Red (1988-2000) is a drop-in final-drive replacement that restores precise power transfer from the transmission to the rear wheels. This complete rear differential assembly eliminates the common wear-induced slop, grinding, and fluid leaks that plague aging TRX300 units, ensuring smooth operation in mud, gravel, and farm lanes. Built for rugged ATV use, it’s designed to be a straightforward, direct-fit fix that keeps your workhorse on the trail and in the field.

This aftermarket rear differential brings tangible value where it matters: robust materials, tested reliability, and compatibility across the TRX300 family. The unit leverages a sturdy aluminum housing with hardened steel gears, delivering long service life under demanding conditions and providing confident torque transfer in tight turns. Thorough testing and quality checks underpin its suitability for trail rides and demanding farm tasks, making it a dependable alternative to original components.

Comprehensive Vehicle Fitment

Product Specifications

OEM & Aftermarket Cross-Reference Information

What's Included

This complete rear differential is packaged as a ready-to-install unit. It includes:

• 1 × Complete Rear Differential

Note: Related items such as mounting hardware or differential fluid are not included.

Why Choose This Aftermarket Replacement?

• Direct-Fit Compatibility: Precisely engineered to bolt into the stock TRX300 chassis and drive setup, minimizing modification requirements during installation.
• OEM Cross-Reference Coverage: Widely cross-referenced to 41300-HM5-A10, 41300-HM5-850, 41300-HC4-000, 41300-HC5-970, ensuring broad compatibility with existing Honda specifications.
• Premium Materials: Aluminum shell with hardened steel gears designed for long life in trail, farm, and worksite use.
• Performance Restoration: Restores torque transfer and differential action that aging units lose, improving handling in turns and under load.
• Quality Assurance: Thorough testing to meet reliability expectations for demanding environments.
• Cost-Effective Alternative: Provides a reliable non-OEM option that delivers durable performance without OEM pricing.

Installation Notes:

• Pre-fill gear oil: Gear oil needs to be added before use; 75W-90 gear oil is commonly recommended.
• Check for compatibility: Confirm part numbers and fitment before installation, as there are multiple 41300 variants across TRX300 models.
• Seal inspection: Inspect seals and mating surfaces for wear or damage and replace as needed to prevent leaks.
• Clean mating surfaces: Ensure the rear housing and mounting points are clean and free of debris to maintain proper alignment.
• Proper alignment: Align the driveshaft and final drive components during installation to avoid binding or premature wear.
• Safety and professional help: If unsure, consult a professional installer to verify installation torque and alignment and to avoid drivetrain damage.

Why Upgrade?

Running a worn-out rear differential on a TRX300 can lead to uneven power delivery, increased drivetrain noise, and eventual failure that leaves you stranded. This aftermarket replacement restores reliable torque transfer, quiet operation, and predictable handling, giving you peace of mind on trails and in the field.