Holden Crewman 2003 Problems

THIS is a common problem. To my knowledge Holden has no solution other than to fit a new diff and hope it is better. Keep up the pressure and demand a fix.

That's the problem when trying to locate the cause of leaks etc. They're not usually the obvious things you think of, like a poorly fitting or damaged seal etc. but you have to check those things first before you dig deeper and spend a lot of money in the process.