However, generally speaking, for a 2000 GMC Sierra you'll likely need either a 75W-90 or 75W-140 gear oil. The 75W-140 is generally preferred for heavier use, towing, or hotter climates. The choice also might depend on the additive package (e.g., limited-slip additive if your truck has a limited-slip differential).
To find the correct oil, you should:
1. Check the sticker on your differential cover: This is the most reliable source of information.
2. Consult your owner's manual: This will have the recommended specifications.
3. Check the axle code: This code is usually found on a sticker in the driver's side door jamb and can be used to determine the correct axle type and oil.
Do NOT guess. Using the incorrect oil can damage your differential. If you're unsure, take your truck to a qualified mechanic or auto parts store and provide them with the information found on the differential or in your owner's manual. They can then help you select the correct oil.
