"W" mode starts you out in second gear, for one, and it may pull timing to reduce torque and horsepower for "Winter" driving. "S" or summer mode starts in first gear, and will give you full power and acceleration, so if there is a bona fide problem with your tranny in first gear, and its not just putting it into autostick mode, you should get it looked at to get the full performance out of your car.