Introducing the Rear Diff Complete for Honda Foreman 4x4 models, a purpose-built aftermarket final gear differential assembly designed to restore confident power transfer and reliable 4x4 engagement on rugged trails and demanding farm work. This complete rear differential fits Honda TRX400FW Foreman from 1996 through 2003 and TRX450FE/FM Foreman from 1998 through 2004, replacing the original OEM unit 41300-HN0-670 to eliminate wear-induced slop and noise. Built from durable aluminum with precision-machined gears and seals, this aftermarket replacement delivers a robust drivetrain upgrade that stands up to hunting, logging, and long days in the field.

This aftermarket rear differential is engineered to tackle the common wear that plagues aging Foreman drivetrains—worn ring and pinion gears, worn bearings, and leaky seals that produce backlash, noise, and uneven power delivery. By swapping in a complete, ready-to-install diff assembly, you gain consistent power transfer to the rear wheels, improved four-wheel-drive engagement, and a quieter, smoother driveline for trail or farm use where reliability matters most.

Comprehensive Vehicle Fitment

Manufacturer	Models / Series	Years / Details
Honda	TRX400FW Foreman (4x4)	1996-2003 • Rear Differential Assembly (4x4) — fits 41300-HN0-670 era models
Honda	TRX450FE Foreman ES	1998-2004 • Rear Differential Assembly (4x4) — compatible with 41300-HN0-670 cross‑reference
Honda	TRX450FM Foreman S	1998-2004 • Rear Differential Assembly (4x4) — compatible with 41300-HN0-670 cross‑reference

Product Specifications

Attribute	Details
OEM Reference Part Numbers	41300-HN0-670, 41300HN0670
Type	Rear Differential / Final Gear Differential Assembly
Manufacturer	Aftermarket Replacement
Application	Honda FourTrax Foreman TRX400FW (4x4) 1996-2003; TRX450FE/FM Foreman 4x4 1998-2004
Material	Aluminum
Differential Gear Ratio	Approximately 13.41:1 (engineered for reliable 4x4 torque transfer; exact ratio varies by model)
Input Spline Count	24
Output / Shaft Spline Count	27
Lubricant	SAE 80 Hyphoid Gear Oil (additional lubrication may be required after install)
Mounting / Installation	Bolt-on rear differential assembly; direct-fit replacement
Notes	Excludes pinion joint (OEM reference 41300-HN0-670 cross‑reference); see cross-reference table for alternatives

OEM & Aftermarket Cross-Reference Information

Part Number	Brand / Type	Cross-Reference Notes
41300-HN0-670	Honda OEM	Direct replacement for Foreman 400/450 4x4; rear final gear differential assembly
41300HN0670	Honda OEM (alternate format)	Direct cross-reference; same fitment as 41300-HN0-670
519-CDI2235F	NICHE Industries	Rear Differential Assembly cross-reference to 41300-HN0-670; compatible with Foreman 400/450 4x4
LDJ2FV	BFO / Aftermarket Replacement	Direct-fit aftermarket alternative for Foreman 400/450 4x4; widely used in the market

What's Included

1 x Complete Rear Differential Assembly

• Notes: Pinion joint is not included with this rear differential (OEM references may exclude the pinion joint). Seals, gaskets, and mounting hardware are not always included; verify contents with your supplier.

Why Choose This Aftermarket Replacement?

• Direct-Fit Compatibility: Precisely engineered to bolt into Honda TRX400FW and TRX450FE/FM Foreman frames without modifications.
• OEM Cross-Reference: Backed by direct cross-references to the Honda OEM 41300-HN0-670, simplifying parts sourcing.
• Premium Aluminum Construction: Lightweight, corrosion-resistant housing that dissipates heat and resists fatigue in tough conditions.
• Enhanced Reliability: Replaces worn gears, bearings, and seals to restore smooth engagement and reduce driveline backlash.
• All-in-One Solution: Complete rear differential assembly designed for straightforward installation and long service life.
• Sturdiness for Tough Environments: Built to withstand trail abuse and farm workload where consistent 4x4 power matters.

Installation Notes:

• Disconnect the battery and ensure the machine is secure before starting work; drain the differential oil before removing the old unit.
• Inspect surrounding mounting surfaces for deformation; clean mating surfaces to ensure a proper seal on the new differential housing.
• When installing, verify the orientation of the differential case and confirm the input/output shaft alignment with the drive shafts; avoid misalignment that could damage gears.
• Replace all seals and gaskets associated with the rear differential housing to prevent leaks; apply a light coat of lubricant to seals during installation.
• Use the appropriate gear oil (SAE 80 Hyphoid) and fill to the manufacturer-specified level after installation; check for leaks after a short test run.
• Confirm 4x4 engagement operation by cycling the transfer case and testing in a safe area before returning to full work duty.

Why Upgrade?

Running a worn rear differential in a Foreman 4x4 leads to increased wear, noisy operation, lash in the driveline, and unreliable four-wheel-drive engagement—precisely the issues that slow you down on the trail or in the field. This aftermarket replacement restores solid gear engagement, reduces noise and heat buildup, and returns dependable, predictable power delivery to the rear wheels, making it a practical upgrade for long-term reliability.