Tech. Info.

Speedometer Information

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. Click here for applications & part numbers.

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)*

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.

	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 gears: 200-4R | TH-350 | TH-400 | 700-R4 | Torqueflite | Ford

GM SPEEDOMETER GEAR INFORMATION

200-4R 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
Click here for part numbers.	31 teeth - white

Notes:

	All 200-4R 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 Street Fighter 200-4R transmissions (Original to Turbo Buick applications).

TH-350 Speedometer Gears

Drive Gears	Driven Gears
7 teeth - pink	18 teeth - brown
8 teeth - orange	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
Click here for part numbers.	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.

TH-400 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
Click here for part numbers.	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 Street Fighter TH-400 transmissions.

700-R4 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
Click here for part numbers.	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
Click here for part numbers.	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
Click here for part numbers.

Notes:

	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.