The speedometer in my GTA is about 3mph too fast (if it says 70, I'm really going 67). If I get down to 50, it's only about 2mph off. Is there anything that can cause this, or do I have to live with it? I'm running stock size tires on the stock wheels. Maybe a factory defect?

 

Any modification to the transmission. Mainly the tail shaft gear?

 

A rebuilt transmission was put in it, but as far as I know the tail shaft was transferred from my original one.

 

I would not worry about it. If you are only off by 5% you are probably right about the average. Every car I have ever had has been off by around 5%, all reading higher than actual. Unless you have a calibrated speedo of course (B4C may have had them, I do not know)...

We notice more today because we have GPSs to give us a real time second opinion on speed. Most people have no idea that they are out at all (unless they have a GPS).

 

Yeah, the only way I noticed it was because of the SpeedView app on my phone. In newer vehicles it's dead on, but in my GTA it's about 3mph off. Maybe they just didn't make them as accurate back then.

 

Old gear driven tech... not 100% accurate ...