Picked up my '91 RS about 2 months ago and the speedo has never worked. Where is the best place to start? Should I replace the speed sensor coming out of the tranny, replace the gauge cluster or ???. Also, the guy I got the car from said that the tranny was rebuilt at some point...is it possible that there is something else that is not connected to mess with the speedo?? This electronic speedo is all new to me, since all my other 3rd gens had the cable...Thanks for any advice you guys may have.
Andy

 

The electronic speedo uses the same drive gear on the tailshaft, but a different driven gear to match with the VSS in the tailshaft.
Its possible when the trans was rebuilt the drive gear on the tailshaft has slipped and is not making contact with the driven gear anymore.
Are you getting an SES light, code 24, for bad VSS signal? If not, it could also be the gears are working and the VSS is sending the right signal to the computer, but the computer is not sending the signal to the speedometer. You'll need to hook up a scan tool and see if the computer is getting a signal from the VSS while the car is moving.

 

I don't have access to a scan tool. The service engine light is almost always on though. If I take it to someone that has a diagnostics scanner would that help firure out where the problem is?