I have a 94 Civic DX with no working speedometer or odometer. Is there a way to tell by looking at the speed sensor if it needs to be replaced?

The shaft wiggles a little but still turns smoothly and doesn't look damaged, the two wings on the shaft look fine.

Alternatively, when this occurs is it generally the speed sensor that needs to be replaced? or is it possible a mechanisim in the transmission housing is at fault?

 

Are you getting a check engine light after driving the car? If yes, the issue points to your speed sensor.

 

My speed sensor looked fine but just died. I found one on Amazon for $16 that has been working fine for several months now. Have you pulled out the gear to see if it's damaged? It's unlikely to break in that area but an easy check.

 

The check engine light comes on, though it takes a few minutes (I have an SRS light on as well). The gear seems fine.

Thanks for the responses. I have a friend with a civic, we're going to do a sensor swap tomorrow.

 

The only thing sensor-related inside the transmission has a plastic ring gear attached to the differential cage that drives the little gear on the sensor. Trouble with it is very rare.