The 1995 Honda FourTrax 300 uses 80W-90 API GL-4 gear oil in its transmission/final drive. Use GL-4 rather than GL-5 to protect internal gears and brass components. This article explains the specification, why GL-4 is recommended, and how to change the oil on a TRX300.
Gear oil specification for the TRX300
Honda’s service documentation for early TRX300 models specifies 80W-90 gear oil with an API GL-4 rating for the transmission/gearcase. GL-5 oils are generally not recommended for these units, as the additives in GL-5 can interact with metals inside older Hondas. When shopping, look for an oil labeled as 80W-90 API GL-4 (and verified compatible with manual transmissions and final drives).
Before using any oil, verify the exact specification in your own bike’s owner or service manual, since production changes or regional variants can occur. In any case, meeting the GL-4 standard and the 80W-90 viscosity is the key requirement for the TRX300’s gear oil.
Here are the key notes summarized for quick reference.
- Gear oil type: 80W-90
- Service rating: API GL-4
- Do not rely on GL-5 unless the manual explicitly allows it
- Any reputable brand that meets the 80W-90 API GL-4 specification is acceptable
Adhering to these specifications helps ensure smooth shifting and long-term reliability of the transmission and final drive in the TRX300.
Maintenance: How to change the TRX300 gear oil
To perform a transmission gear oil change on the TRX300, follow these steps. This will help you maintain proper lubrication and prevent gear wear.
- Warm up the engine briefly to ensure the old oil flows out smoothly.
- Place the ATV on a stable stand or jack and position a drain pan under the transmission drain plug.
- Remove the transmission drain bolt and allow the old oil to drain completely.
- Clean the drain plug and reinstall it with a new sealing washer or gasket, tightening to the specified torque in the manual.
- Remove the fill plug on the transmission case.
- Using a funnel, fill with fresh 80W-90 API GL-4 gear oil until it begins to run out of the fill hole, then stop and reinstall the fill plug.
- Wipe away any spilled oil, lower the ATV, and run the engine for a short period to circulate the new oil. Recheck the level and look for leaks.
Note: The TRX300’s transmission oil capacity varies by model year and configuration. Always consult the owner’s manual or service manual for the exact oil capacity and fill procedure specific to your bike. If in doubt, err on the side of adding oil until it reaches the fill hole level, then secure the fill plug and clean the area.
Additional notes: compatibility and common pitfalls
Why not GL-5?
GL-5 gear oils contain additives that can corrode or cause excessive wear on certain brass or bronze components inside older Honda transmissions. For the TRX300, sticking with GL-4 80W-90 helps prevent these issues and aligns with factory specifications.
Other considerations
A few additional tips to keep in mind:
- Avoid mixing different oil brands or viscosities; stick to the recommended 80W-90 GL-4.
- Do not overfill the oil; overfilling can cause foaming and pressure issues.
- Keep the oil clean and use a fresh fill whenever you perform a drain and fill.
Following these guidelines will help ensure the longevity and reliable performance of the 1995 TRX300’s transmission and final drive.
Summary
The 1995 Honda FourTrax 300 requires 80W-90 API GL-4 gear oil for its transmission/gearcase. Avoid GL-5, unless explicitly approved by Honda for your specific model. When changing gear oil, drain the old oil completely, refill through the fill plug with fresh 80W-90 GL-4 until the level is correct, and consult the manual for exact capacity and torque specifications. Regular maintenance with the correct oil helps preserve shifting smoothness and drivetrain longevity.