I'm having a hell of a time trying to get my speedometer working in my Shelby Lancer after it had sat for a long time. Ever since getting the car running again last year, the speedometer (mechanical cable driven) jumps around all over the place, or it's seemingly dead with the needle stationary below 0, or when it does work, it reads about 25 MPH too fast. I also hear a faint jingle sound from the cluster, like a tiny bell ringing randomly when I drive it which seems to coincide with the needle jumping all over the place. I have another H-body instrument cluster (original from the car) and it does the same thing including the ringing sound.

I know my speed sensor and drive gear is OK. The cables I'm not too sure about. It uses an extension cable which I tried removing and no difference.

I'm not sure if this means the speedometer is broken, but maybe the best fix is to get an electronic cluster from an '89 H-body car and get rid of the cable entirely?