The correct lubricant depends on the rear axle ratio and the climate. Your owner's manual will specify the recommended lubricant. It will likely be a specific weight of gear oil, often something like 75W-90, 75W-140, or 80W-90. Some differentials may even require a limited-slip additive if they have a posi-traction or limited-slip differential.
To find the correct lubricant:
1. Check your owner's manual: This is the best place to start.
2. Look for a sticker on the differential: Sometimes the axle ratio and recommended lubricant are indicated on a sticker on the differential housing itself.
3. Check the differential tag (if present): This tag is usually located on the differential and will give more precise specifications.
4. Consult a parts store: Provide them with the year, make, model, and engine size of your truck, and they can look up the correct lubricant for your rear differential.
Using the incorrect lubricant can lead to premature wear and even catastrophic failure of your rear differential. Always use the recommended lubricant as specified by the manufacturer.
