Um your car is not limited to what the speedo says. How fast your car can go depends on alot of things mainly hp/tq and gearing. The higher gears you have the faster your car can go untill it hits the redline. But you also have to have the hp/tq to make the car pull the gears. In other words it is technically possible to gear a car so high it cannot pull itself. On the other hand you can gear your car so it can go though all 4 gears in 30 seconds but it may only go 70mph but u will get there fast. That is how alot of cars go so fast in the quarter mile but only have 400 to 500 hp