Drivetrain & Track
Transmission Gear Ratio & Speed Chart
Plot speed vs. RPM curves across 1st–6th gears to optimize shift points, final drives, and top speed.
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How to Use This Tool
- Enter tire diameter or use the tire size helper values.
- Set redline RPM, final drive ratio, and each gear ratio (or load a preset).
- Review max speed per gear at redline and RPM drop on upshift.
- Use the chart to pick shift points for track or highway cruising.
The Formula & Physics Behind the Math
Speed (MPH) = (RPM × tire diameter × π × 60) ÷ (gear ratio × final drive × 63,360). RPM at speed is the inverse. RPM drop on upshift = redline × (next gear ratio ÷ current gear ratio). Lower gearing raises acceleration but reduces top speed in each gear.
Frequently Asked Questions
What final drive should I use?
Check your factory spec or diff tag. Common RWD swaps: 3.73, 4.10, 3.42. A shorter (numerically higher) final drive multiplies torque but lowers top speed per gear.
How do I find my tire diameter?
Use the Tire Size Calculator on this site, or measure loaded radius × 2. Stretched tires and wear change effective diameter slightly.
Can I model a 5-speed or 8-speed?
Yes — leave unused gear fields at 0 or 1. Only gears with ratios above zero are plotted.