ok i changed my tranny and before i changed it the spedomiter worked fine and now that i changed it it dont work i changed the sensor and everything anyone have any clue what it could be

Did you re hook up/ check the VSS? Thats what tells the speedometer how fast your going and if its bad or not hooked up it wouldnt work.

vss?i pluged both of the sensors on the tranny back up

VSS = vehicle speed sensor. I would guess its bad.

it is the back sensor on the tranny correct? if so i changed it

I'm not sure where it is, but it controls the speedometer, and either its bad or theres a lose/cut connection.