What kind of rear axle oil for gmc truck?

For a GMC truck, the recommended rear axle oil typically depends on the specific model and year, but a common choice is 75W-90 or 80W-90 gear oil. It's essential to use a high-quality oil that meets or exceeds the API GL-5 specification for optimal performance and protection. Always consult your owner’s manual for the exact specifications and recommendations for your particular model. Additionally, if your truck has a limited-slip differential, consider using a gear oil formulated for such applications.