[MrForbes]

I've worked on cars for years....the gears used in automotive transmissions and differentials are made of very very hard steel, and will last for a very long time with proper lubrication. Without lubrication, they will be destroyed in a matter of miles (I've done it myself by forgetting to add oil to a differential on a car I built).

Use grease! add a little more grease if you aren't sure exactly how much you need.