Yes it is the gearing, but the speed at which the motor turns makes a HUGE difference too, as the gearing is tailored to the RPM range of the motor and where the powerband is. Larger displacement/output means less RPM required to get things moving, which is why big V8s can cruise the freeway at 3K RPM on the freeway at 80mph, while we are much higher. I didn't mean to say it has "nothing" to do with gearing.