Gear Ratios

This ratio tool is broken down into Simpson, Ravenaux, overdrive and undersrive gear sets. The tool allows you to calculate gear ratios on a wide range of transmissions. The basis of the calculator is the three-speed Simpson or Ravinaux gear set. Many late-model transmissions use a combination of these gear sets and the overdrive (or underdrive) set to achieve the various ratios. Once you understand the combinations of gear sets being used you easily calculate all the ratios of the transmission. This tool comes in handy for performance applications where you’re considering a change in gear sets and need to know the ratios for each range.

Ravigneaux Tooth Counts
Small Sun Gear
Large Sun Gear
Ring Gear


Ratios
First Gear 2.40
Second Gear 1.47
Third Gear 1.00
Fourth Gear 0.67
Reverse 2.00
Simpson Tooth Counts
Input Ring Gear
Input Sun Gear
Reaction Sun Gear
Reaction Ring Gear

Ratios
First Gear 2.74
Second Gear 1.57
Third Gear 1.00
Reverse 2.07

Overdrive Planet Tooth Counts
Sun Gear
Ring Gear
Ratio
Overdrive 0.75

Underdrive Planet
Tooth Counts
Sun Gear
Ring Gear
Ratio
Sun as Input 2.76
Ring as Input 1.57