To be absolutely certain, check your owner's manual. This is the best source of information for your specific vehicle. The manual will list the recommended oil weight (like 75W-90, 80W-90, etc.) and type (GL-4 or GL-5).
If you don't have the owner's manual, you can:
* Check the transmission case itself: Sometimes the recommended oil type and weight are stamped or stickered on the transmission housing.
* Consult a local parts store: Provide them with your truck's year, make, model, and engine, and they can look up the correct transmission oil. Bring your VIN if possible for added accuracy.
Important Note: Using the wrong type of gear oil can damage your transmission. GL-5 is generally more aggressive and may contain additives that can harm the softer brass synchronizers found in some manual transmissions. While some GL-5 oils are backward compatible with GL-4 applications, it's always safest to use what's specifically recommended by the manufacturer.
