1. Park the truck on level ground and engage the parking brake.
2. Locate the differential fluid fill plug. It is typically located on the side of the differential housing, near the top.
3. Clean the area around the fill plug with a rag to prevent dirt from entering the differential.
4. Remove the fill plug with a wrench.
5. Insert your finger into the fill hole to check the fluid level. The fluid should be at the same level as the hole.
6. If the fluid is low, add enough new fluid to bring the level up to the fill hole.
7. Replace the fill plug and tighten it securely.
