* Type of lubricant: This will likely be a gear oil, often specified by API (American Petroleum Institute) classification (e.g., GL-5). Do not use grease.
* Viscosity: This is a measure of the oil's thickness, and is usually specified with a number (e.g., 75W-90, 80W-90). This will depend on your climate - heavier viscosities are used in hotter climates.
Finding the correct lubricant:
1. Check your owner's manual: This is the best source of information.
2. Look for a sticker on the differential cover: Often, the recommended gear oil will be listed here.
3. Check the differential tag: The differential tag, usually located on the differential housing, might provide information about the gear ratio and recommended lubricant.
4. Consult a parts store: Provide them with your truck's year, make, model, and rear axle ratio (if you can find it), and they can help you choose the correct gear oil.
Using the wrong lubricant can severely damage your rear differential, leading to costly repairs. It's crucial to use the correct type and viscosity of gear oil.