I ran split gearbox designs on each of my cars in the last race. Both have exactly the same stats and finetune potential, but vastly different weights +/- 10kg. The heavier gearbox was clearly quicker than the lighter, so go figure?
Perhaps one driver is much better than the other Jason? Also if the gearbox was 10kg heavier then im assuming the car it was in was 10kg heavier than the other, it wasnt balanced out with other parts?
A test like that can only really be done during testing where everything is identicle bar the gearbox itself.
My fastest driver (Albus) had the lighter car and got beat by my slower driver (Ozkaya) in the heavier car in quali last week. Albus got up in the race but only by 0.3sec... I know there are other factors in a race, but like Dan said, it doesn't add up.