# Driven Teeth =[(# Drive Teeth)*(Axle Ratio)*(Tire Revs/Mile)]/1000

This tool is a little quicker. To figure out your speedo gear, you'll need to know the number of drive teeth on the gear in your transmission. For an '89 - 93 Mustang, it is typically 8. You'll also need to know your tire diameter in inches. Punch in the figures below and hit the calculate button to find out the proper gear.
Notes:
7 teeth - T-5’s - 83-89 & 96-98 Cobras with T-45
8 teeth - T-5’s - 90-95 & 96-98 Mustang GT with T-45 & All AOD's

Drive Teeth	Gear Ratio	Tire Size (inches)

Speedometer Gear:

Internal Manual Trans. Drive Gears (17285)

Manual Trans.
Drive Gears (17271)

Auto Trans.
Drive Gears (17271)

Teeth

Color

Part#

Teeth

Color

Part#

Teeth

Color

Part#

6

Black

E3ZZ-B

Wine

C0DZ-A

16

Blue

D0AZ-A

7

Yellow

E3ZZ-A

17

White

C3DZ-C

17

Green

C7SZ-A

8

Green

F0ZZ-A

18

Yellow

C0DD-B

18

Gray

C7SZ-B

19

Pink

C0DZ-B

19

Tan

C7VY-A

20

Black

C1DZ-A

20

Orange

C8SZ-B

21

Red

C4OZ-A

21

Purple

D0OZ-B