My Speedometer is 10mph fast in my 1998 Z28. Anyone have any ideas where to start???? I have stock final drive gears and stock tire size.

 

Same problem in my 93.

 

common inaccuricies from the factory. i think its a secret plan to make people think theyre speeding when they are actually going the speed limit. my blazer is 7 mph fast at highway speed, and my bike is as much as 20 fast at speeds above highway limits