How often should a ball differential be rebuilt? I see guys at the track doing it all the time but I just play with my car and it seems fine even though I’ve never had it apart.
Ain’t broke, don’t fix. A ball diff can go a long time between rebuilds as long as it is kept properly adjusted. Slipping due to a too-loose setting is what kills ball differentials. If your car screeches or barks when you accelerate, it’s likely the differential slipping. If left unchecked, the diff balls will score the diff rings. Then you’ve got a vicious cycle of rough rings damaging the balls, which causes more damage to the rings, which eats up the balls … and then you need to rebuild. If your diff turns easily, doesn’t feel gritty when operated by hand, and doesn’t slip in use, then keep driving. If not, rebuild it with fresh rings and balls. A complete rebuild kit will only cost you about $15.
It’s normal for the diff balls to polish a bright line on the diff rings. If you can feel a groove, the ring is worn. Flip it over to reveal a fresh surface or replace it.
A diff rebuilt kit will restore like new performance. Check the parts list in your manual.