2 Once you unbolt the cover from the axle and have it cleaned up a bit, check the gasket face for any sign of warpage. It’s not uncommon to have the bolt holes flared inward slightly. You can fix this by tapping them back flat as shown here with a rounded steel rod and a piece of tube held behind the cover. Check the cover on a flat surface to ensure it is straight. As a final check at the bolt holes, sandpaper can be used to check for high spots.