help me please!!!

i am trying to find out how to convert my oldstyle automatic transmission to a electronic digital spedometergauge. I got these gauges from my buddy but i need to no what the thing is called that hooks to the tranny and to the gauge to tell you what speed your going. any help pics of what it is will be very helpful.

come on guys any input i have no clue

it replaces the spedometer i know that but it converts the oldstyle spedometer to an elctric spedometer what is it called.

try google, hers a link i found in seconds with some good information. good luck, i know nothing about it so here you go.

http://www.electro-tech-online.com/general-electronics-chat/1030-electronic-speedometer-using-stepper-motor.html

speed sensor

thanks guys i found what i need to get from jegs thanks.