What would make the speedometer stop working now and then and not shift right.?

Question

Our 93 taurus wagon has an intermittent problem.It doesn't shift smoothly when the spedo stops working.

Answer 1

I don't know why people that don't have a clue start guessing.  Your "check engine" light is on.  I know this not because I'm omniscient but because a faulty speed sensor (located in/on the transmission) will set a hard code.  This will cause the symptoms that you have described.  Many parts stores will read/clear fault codes free.  It may be that the sensor wiring has been damaged by someone s******g around under the hood installing useless 'speedy' gimmicks, but if the car has not been violated as such you probably just need a new sensor.

Answer 2

most likely electrics.  

Answer 3

the speedo is read off the abs module, so that is also where the trans get it's shifting signals, you will need to find the fault in the abs priopr to the transmission, suspect a wheel speed sensor