I know... Another Speedometer question...

[iBaSiiCK]

I've searched in and out of every 240sx forum out there for the past 5 months and came out empty...

The problem I'm having is that my speedo doesn't work when driving 0-58mph but when I hit 59mph it starts working but reads 80mph.. and what stumps me is that my odometer and trip work 100% of the time so that should rule out a faulty speed sensor shouldn't it? Also last summer when it was hot and humid the speedo worked every once and awhile but the needle would slightly twitch when accelerating.

Any insight of my problem would be greatly appreciated
Thanks