This is on my 05 Liberty's front diff. It's an aluminum diff, steel fill plug (just uses the drive end of a 3/8" ratchet). Just tried it with the vehicle dead cold (been sitting for a few days) and it seems pretty tight. Didn't want to force it. I'm thinking I should drive it and get it up to temp so that the aluminum expands (expands faster than steel I think?) and then that might allow it break free easier. Does that seem logical? Thanks!