Sorry I do not understand your weight/force analogy. I assume that in a car, both sides have equal weight/inertia. Anyway, I did write "approximately" to avoid

Sorry I do not understand your weight/force analogy. I assume that in a car, both sides have equal weight/inertia. Anyway, I did write "approximately" to avoid discussing acceleration/inertia of the differential itself. I should have written "in steady state" or something like that. It is true that a complete discussion can be more involved