Goodheart-Willcox Co., Inc.

Gear Drive

Small gear driving a larger gear

Goodheart-Willcox Co., Inc.

Gear Drive

Large gear driving a smaller gear

Goodheart-Willcox Co., Inc.

Gear Ratio

The number of revolutions a drive gear

must turn before the driven gear

completes one revolution

Calculated by dividing the number of

teeth on the driven gear by the number

of teeth on the drive gear

Gear Ratio = # of driven gear teeth

# of drive gear teeth

Goodheart-Willcox Co., Inc.

Gear Ratio

If the drive gear has 12 teeth and the

driven gear has 24 teeth, the gear ratio is

two-to-one

Gear Ratio = # of driven gear teeth

# of drive gear teeth

= 24

12

= 2 or written 2:1

Goodheart-Willcox Co., Inc.

Gear Ratio

Goodheart-Willcox Co., Inc.

Transmission Gear Ratios

First gear 3:1

Second gear 2:1

Third (high) gear 1:1

Reverse gear 3:1