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Speedometer Gears

Formula for Calculating Speedometer Gears

The following formula will work for any GM, Ford or Chrysler vehicle and is very useful when there is no established baseline from which to work from such as replacing a transmission in a vehicle that was purchased without a drive line. The accompanying charts show what gears were manufactured for each type transmission. TCI® now stocks the most popular speedometer gears.

Note: Drive gear refers to the gear that is on the transmission output shaft. The driven gear is located in a removable housing usually in the tailhousing of the transmission. Be aware that some transmissions will have different driven gear housings depending on the tooth count of the driven gear.

# Drive Teeth X Axle Ratio X Tire Rev. per Mile = # Driven Teeth
1001

Use the following formula to calculate the Tire Rev. per Mile for the above formula.

Tire Rev. per Mile = .             20168             .
Tire Diameter (inches)

Speedometer Gear Calculator

Try this handy custom calculator. It will do all the work for you. If you don't know your tire diameter, calculate it below using the P-metric sidewall designation.

# of Drive Teeth:
Axle Ratio:

Tire Diameter:
# of Driven Teeth:

 Tire Diameter Calculator

Tire Diameter Calculator  
Tire Width
(mm)
Aspect Ratio
(1-100)
Wheel Diameter
(in)
  Tire Diameter
(in)
 
Enter the tire width in millimeters, the aspect ratio, the wheel diameter in inches, and
Click on Calculate...

Speedometer Gear Charts

Speedometer gears: 2004R | TH350 | TH400 | 700R4 | Torqueflite | Ford

 

GM SPEEDOMETER GEAR INFORMATION

2004R Speedometer Gears

Drive Gears Driven Gears
10 teeth - green 26 teeth - brown
11 teeth - orange* 27 teeth - black
12 teeth - red 28 teeth - yellow
13 teeth - white 29 teeth - green
  30 teeth - blue
  31 teeth - white

Notes:

- All 2004R transmissions use a 1" diameter steel driven gear housing.
- The drive gear is part of the governor assembly which is located inside the oil pan. The gear can be replaced separately by removing the retainer clip on the governor shaft.

* - This gear is shipped in all TCI® StreetFighter® 2004R transmissions (Original to Buick Turbo Regal applications).

 

TH350 Speedometer Gears

Drive Gears Driven Gears
7 teeth - pink 18 teeth - brown
8 teeth - black 19 teeth - natural
9 teeth - green 20 teeth - blue
10 teeth - red or purple 21 teeth - red
17 teeth - red 22 teeth - gray
18 teeth - blue 34 teeth - light green
19 teeth - yellow 35 teeth - orange/pink
20 teeth - brown 36 teeth - white
  37 teeth - red
  38 teeth - blue
  39 teeth - brown
  40 teeth - black
  41 teeth - yellow
  42 teeth - green
  43 teeth - purple
  44 teeth - dark gray
  45 teeth - light blue

Notes:

Chevrolet transmissions use a 1" diameter steel driven gear housing located in the tailhousing on all two-wheel drive applications.
Buick, Oldsmobile & Pontiac transmissions use a 2.078" diameter driven gear housing. Two housings, each made from either aluminum or plastic, are available for driven gears with 34 or more teeth. One fits gears from 34 - 39 teeth and the second one fits gears from 40 - 45 teeth.

 

TH400 Speedometer Gears

Drive Gears Driven Gears
7 teeth - red 16 teeth - (truck)
8 teeth - black 17 teeth - (truck)
15 teeth - brown or gray* 18 teeth - (truck) code H
16 teeth - orange 19 teeth - (truck) code J
17 teeth - red 20 teeth - (truck) code K
18 teeth - yellow or blue 21 teeth - (truck) code L
19 teeth - yellow or white 22 teeth - (truck) code M
20 teeth - green 34 teeth - light green
21 teeth - black 35 teeth - pink
  36 teeth - white
  37 teeth - red
  38 teeth - blue
  39 teeth - brown
  40 teeth - black
  41 teeth - yellow
  42 teeth - green
  43 teeth - purple
  44 teeth - dark gray
  45 teeth - light blue

Notes:

Two aluminum housings are available for driven gears with 34 or more teeth. One fits gears from 34 - 39 teeth and the second one fits gears from 40 - 45 teeth.
The driven gear housings go in the case just forward of the tailhousing.
* - This gear is shipped in all TCI® StreetFighter® TH400 transmissions.

700R4 Speedometer Gears

Drive Gears Driven Gears
15 teeth - gray 18 teeth - (truck) brown
17 teeth - red* 19 teeth - (truck) dark aqua
18 teeth - blue 20 teeth - (truck) silver
19 teeth - yellow 21 teeth - (truck) red/chartreuse
20 teeth - brown 22 teeth - (truck) gold
  23 teeth - (truck) maroon
  24 teeth - (truck) dark blue
  34 teeth - light green
  35 teeth - orange/pink
  36 teeth - white
  37 teeth - red
  38 teeth - blue
  39 teeth - brown
  40 teeth - black
  41 teeth - yellow
  42 teeth - green
  43 teeth - purple
  44 teeth - dark gray
  45 teeth - light blue
* - This gear is shipped in all TCI Street Fighter 700-R4 transmissions.

Notes:

- Two 2.078" diameter housings, each made from either aluminum or plastic, are available for driven gears with 34 or more teeth. One fits gears from 34 - 39 teeth and the second one fits gears from 40 - 45 teeth.
- The driven gear housings go in the tailhousing assembly on all two-wheel drive applications.

 

CHRYSLER SPEEDOMETER GEAR INFORMATION

 

Torqueflite Speedometer Gears

Drive Gears Driven Gears
13 teeth - machined into output shaft 25 teeth - light green
  26 teeth - red
  27 teeth - beige
  28 teeth - light blue
  29 teeth - black
  30 teeth - yellow
  31 teeth - green
  33 teeth - yellow
  34 teeth - green
  35 teeth - orange
  36 teeth - red
  39 teeth - green
  40 teeth - orange
  41 teeth - red
  45 teeth - yellow

Notes:

All Torqueflite transmissions use a 1.75" diameter driven gear housing.
The driven gear housings go in the tailhousing assembly on all two-wheel drive applications.
The housing must be placed in the correct orientation for the particular driven gear being used. The three positions broken down by tooth count are; 25-31, 32-38, 39-45

 

FORD SPEEDOMETER GEAR INFORMATION

 

Ford Speedometer Gears

Drive Gears Driven Gears
6 teeth - machined into output shaft (C6 only) 16 teeth - tan
7 teeth - machined into output shaft 19 teeth - tan
8 teeth - machined into output shaft 20 teeth - orange
9 teeth - machined into output shaft 21 teeth - red
  23 teeth - white 1
 
   

- Ford drive gears are machined into the output shaft on C3/C4/C5/C6 & AOD transmissions. You may need to remove your tailhousing to determine how many drive teeth your transmission has.
1 - This is a retrofit gear to allow the speedometer to function with 3.73 and 4.10 rear end gears. Since the gear tooth pitch is slightly different than OE, the service life of this gear is limited to less than 25,000 miles.