My engine RPM is at 3400 going 75mph. I'd like to see the engine RPM at 2900 or 3000 going 75mph. That will still keep the engine in the passing torque range in 5th gear...or keep the 5th gear and add a 6th gear to reduce that RPM. That's why EPA rates the gas mileage on the automatic higher than on the manual. It'll keep the cabin noise down a bit, and decrease engine wear. The scion designers could have thought about that before putting it into production (lower 5th gear ration), else we wouldn't be having this discussion. It wouldn't increase the car price by just changing the gear ratio.

hmmnn.....I guess I could throw on some larger tires to decrease ratio...

 

The reason they made the 5th gear so short relative to most cars is to increase top end acceleration, of course. I've never ran a true 1/4 mile before, but do you shift into 5th gear near the end? If so, then it will decrease the amount of time it takes = faster times.

 

For a 1/4 mile, you don't need to shift to 5th gear. 4th gear can go to about 110mph..... So, with such a 4th gear like that, it will be no problem to pass in 4th gear. I find myself when entering the freeway or accelerating to a cruising speed to shift 1-2-3-4, and the quickly shift from 4th to 5th because the darn 4th gear ratio is so close to the 5th gear that it almost makes the 5th gear unless. Therefore, lowering the 5th gear ratio to 75mph at 2800 or 3000 RPM will be a good compromise on the manual. Look at the automatic....its RPM is low at 75mph as from other posts and people have no problem with that. Overall, the engine will wear less, you'll have a more quiet ride, and you'll still have smooth power with that slightly less gear ratio in fifth gear....a 6th gear.