speedo glitch

My speedo is messed up on my 90 SC. If the car sits for awile the speedo will not work at the begining, but after awile it will work properly again. The main problem is that it does not increase the milage on the odometer. Is it the speed sensor in the tranny, or something else?

Thanks!
Shane

I had kinda the same problem. My old 120 speedometer would work but the odometer wouldn't work, it just quit one day. I bought a 145 speedo and installed it. Everything works now, speed and mileage. So my conclusion is that your speedo is TOAST!

Cheers,
Calvin