I got my 1990 Turbo Grand Prix about 2 months ago. It had about 68K on it. As far as I know it is basically all stock. So far it is running great. But one thing I noticed is that the speedometer on the dash and the HUD are not the same. My speedometer on the dash would bottom out at 120 but the HUD would only say 110. The difference is exponential though. the faster I go, the larger the difference is. The speedometer would say 60 and the HUD would say 55.
What one is the correct speed? As far as I am concerned, the speedometer on the dash is correct. :wink: But if a cop asks, I go by the HUD. :D Is this a common thing? Is it easy to fix?
That's normal. Mine is like that also. If you watch at very low speeds,(15 and below) the hud may be higher than the dash. Around 25 - 30 m.p.h they even out more and after that the hud is slower. The hud is actually the most accurate I believe. I know when I got pulled over last Nov. the cop said I was doing 74, and I remember the dash saying just below 80.
Mine does that very same thing, i thought it was off.