I always had issues with rear end seepage after a few months of racing . The bolts, even though they are self locking with Loctite always pounded out the gasket and leaked .. This gasket ends all that. It's a steel shim with reusable gasket material on both sides... and their cheap ..
Lube Locker Ford 9" Differential Gasket
https://www.amazon.com/Lube-Locker-F...ds=Lube+locker