⚙️ Ball Differential
A differential using small balls squeezed between two thrust plates, where the diff action is set by how tightly you screw it down.
Common on 2WD racers and adjustable without opening the car up, but the balls, rings and grease wear and need rebuilding far more often than a gear diff.
What it actually does
A ball differential transfers power through small steel balls squeezed between two plates, with the pressure set by a spring and adjusting nut. Tightening or loosening that nut changes how much the diff can slip, giving a smoothly adjustable amount of limited-slip behaviour.
In practice
They are common on 2WD racing buggies and on-road cars because they are light, easy to adjust trackside and very smooth. The correct setting is tight enough that the diff does not slip under power, and no tighter.
Worth knowing
Ball diffs are a maintenance item. Grit or worn balls cause notchy, inconsistent action, and a diff that slips under acceleration will destroy its own plates quickly — rebuild it rather than winding the nut tighter.