4wd slotSlot.it supply their e-Tron Quattro with the front pulley one tooth larger than the rear one, which ensures that the front axle spins whenever the rear one does, but always slhtly slower, giving a rear-drive bias.A 4WD car with a dual shaft motor can be easily converted for testing to 2WD by removing the front pinion. Then lap times can be compared. The same can be done with a belt drive car by