speedometer ratio

[whitelightenin69]

Does anyone know what the speedometer ratio of a 69 c10 is?
I'm trying to find out what speedometer gears I need for a 700r4 with 28" tall tires and 3.73 gears.

[Palf70Step]

It depends on what the 700R4 came out of and what gear it has on it'd output shaft. These are some notes I picked up from some

Twelve speedometer driven gears are available for the 700R4 / 4L60 transmissions to calibrate the speedometer with various axle ratios and tire diameters. The number on the driven gear housing must match the number of teeth on the driven gear. Unless driven gears with more than 45 teeth and / or drive gears with fewer than 15 teeth become available, it will be impossible without using a ratio adapter to have an accurate speedometer with rear end gear ratios lower (higher numerically) than 4.10:1, unless 27 inch or larger tires are installed.




With 15 Tooth Drive Gear
Axle Ratio Tire Height Driven Gear Teeth
4.56 33 42
4.56 35 39
4.10 26 45 will work, but will read about 3 MPH fast at 50 MPH.
4.10 27 45
4.10 28 44
4.10 29 43
4.10 30 41
4.10 31 40
4.10 33 38
4.10 35 35
3.73 26 43
3.73 27 42
3.73 27 1/2 41
3.73 28 40
3.73 29 39
3.73 30 38
3.73 31 36
With 17 Tooth Drive Gear
Axle Ratio Tire Height Driven Gear Teeth
3.73 28 45
3.73 29 44
3.42 26 45
3.42 26 1/2 44
3.42 27 43
3.42 28 42
With 18 Tooth Drive Gear
Axle Ratio Tire Height Driven Gear Teeth
3.23 26 45
3.23 26 1/2 44
3.23 27 43
3.23 28 42


You can also get a lot of info from this board members site
http://www.73-87.com/7387garage/drivetrain/speedo.htm