92 sonata - broken speedometer and odometer..

one day i started up the car and while i was driving i noticed the speedometer and odometer were not functioning. i went to the mechanic, and he said i needed a new transmission?... so i figured i'd ask here because i'm pretty sure the issue could be wiring/ground related.

any thoughts?

nope, the speedometer is mechanical, it plugs in the differential area, I had the same problem and the differential was shot = new transmission.