What is the gear ratio when the car is being driven at the to gear(to speed)?

When discussing gear ratios and their impact on a car's performance, particularly in the context of achieving top speed, here are some key points to consider:

Gear Ratio and Speed

• A lower gear ratio (e.g., 6:1) generally provides more top speed because it allows the engine to reach higher RPMs more efficiently. This is often referred to as a "high" or "tall" gear ratio5.
• Conversely, a higher gear ratio (e.g., 9:1) provides more torque but sacrifices top speed. This is typically referred to as a "low" or "short" gear ratio5.

Gear Ratios in Different Gears

• For a car to achieve optimal top speed, the gear ratios should be set such that the engine operates within its optimal power band. Here is an example of gear ratios optimized for top speed and general performance:
  • 1st: 2.56
  • 2nd: 1.8
  • 3rd: 1.3
  • 4th: 1
  • 5th: 0.8
  • 6th: between 0.7 and 0.6 (e.g., 0.660)1.

Final Drive Ratio

• The final drive ratio also plays a crucial role in determining the car's top speed. A lower final drive ratio (e.g., 3.9) is better for top speed, while a higher final drive ratio (e.g., 4.6) is better for acceleration but sacrifices top speed3.

Calculation

• To calculate the combined gear ratio, you multiply the gear ratio of the transmission by the final drive ratio. For example, in first gear with a transmission ratio of 3.636 and a final drive ratio of 3.9, the combined gear ratio would be (3.636 \times 3.9 = 14.1804)3.

In summary, when driving at top speed, the gear ratio should be optimized to keep the engine in its power band while allowing for the highest possible RPMs, typically achieved with lower (or taller) gear ratios and an appropriate final drive ratio.