What oil do you use in your 1999 Ford F-250 4x4 limited slip differential?

For a 1999 Ford F-250 4x4 with a limited slip differential, it's recommended to use an 80W-90 or 75W-140 gear oil that meets API GL-5 specifications. Additionally, it's important to add a limited slip additive to ensure proper operation and prevent chattering during turns. Always check the owner's manual for specific recommendations and capacities.