The manual will specify the recommended weight, which is typically either 75W-90, 75W-140, or possibly another specification. Using the incorrect weight can damage your rear differential.
Do not rely on general advice found online; always consult your vehicle's documentation. Providing the rear axle ratio (e.g., 3.55, 3.92, 4.10) might help others give a more informed guess, but it's still no substitute for checking your vehicle's specifications.