performance does matter to me but I hate driving a 2000 mile road trip the putting the car up on stands and pulling the diff out and changing from the 2.76 gears I have to the 3.91s that are perfact for me for the 1/4 and driving for the weekend then changing back to drive home not to mention having the 3rd member roll around in the trunk and smash out my 1/4 pannels. Thoses guys might think you will loose 1 second in the 1/4 but PROVE IT! I will be going from the 3.23 gears I have now that arent that good for the 1/4 and suck on the highway reving 2800 at 60mph to 3.91 that are perfact for the 1/4 and will rev 2350 on the high way in overdrive. I took my overdrive compleatly apart last night and found the overdrive section is heavy like ~20 pounds and that is spinning weight (which on an inertia dyno will show less horsepower but wont make a difference on a steady load dyno both taking readings from the rear wheels) As for the "you should be driving in you peak tourque for best mileage" topic (this topic will probably come up soon) it is also not true simply because the engine is more powerfull then the car needs. I could understand it being true with a engine designed for the car to be delivering the best gas milage. So in conclusion if you build the whole car to use the overdrive properly it can show gains in milage and performance!