spedo gear

[smurfee]

   I am getting a new spedo cable from NAPA, I have a 302 - C6 in my 57 custom- how mant teeth do I need on the plastic gear that goes into the trans? SMURFEE

[lalessi1]

I have been told that 1000 RPM on the speedometer cable should read 60 mph on the speedometer by design. The number of teeth on the speedo drive gear, the number of teeth on the speedo gear inside the transmission, the rear end ratio and the tire size all factor in. The calculation of the constant is a little long but simple.

Number of teeth on speedometer driven gear = 20.168 / tire dia (inches) X rear end ratio X number of teeth on the 
   speedometer drive gear

For example a 27" diameter tire with a 6 tooth internal transmission speedometer drive gear and a 3.89 rear gear would need   
             20.168/27 x 3.89 x 6 = 17.4 teeth... 17 or 18 tooth driven gear. 17 would read a little high, 18 a little low.

   

[Lincoln4002]

If thats a pic of your 57, I have some spare parts you mighyt be interested in.

[smurfee]

lincoln 4002 thats my car, what things are you talking about

[JPotter57]

Long time no see Don...where ya been hidin'?

[smurfee]

HI JAY, been here, just not talking - thanks for caring

[RICH MUISE]

Jpotter=James