I assume you are talking about the tuning transmissions, no?
The close ratio gearbox shortens the gear ratios and thus gives a better acceleration at the expense of top speed. However, many stock cars have moderate amounts of power and could never reach the top speed with the original gearbox so this enables you to use the engine power more effectively.
The super close gearbox is like the close ratio one but the impact is even greater. It occasionally comes with an extra gear.
The fully customizable gearbox allows you to set up the gearing just the way you want, the ratio of every single gear (and the final ratio) can be made shorter or taller. It's the ultimate tool in utilizing the powerband of your car, making very efficient use of the engine power - but only if you know how to tune it.
When you talk about the "slowing down" you probably mean a lower top speed, but at the same time the acceleration has improved. You will need to decide which one you want, you can seldom get a car with excellent acceleration and brilliant top speed unless it has a great amount of power. In lower powered cars, compromises are needed.
- R -
