My Speedometer pointer needle is sitting a 5 MPH when car is in park, when I'm driving it is reading 5 mph above my actual speed.
I have had this car for about 30 years, but only just started driving it again after sitting 15 years before restoring the Chassis. I don't remember it being an issue before.
I was wondering if there is a way to calibrate the speedometer so it is reading accurately.
I cant find anything online or in the CSM discussing this.
It is a stock 72 cutlass supreme, all original Th350 trans and 10"rear-end with original 14" ssII wheels, No upgrades
any suggestions or ideas would be greatly appreciated

 

Because of the tolerances involved , and the specialized equipment needed , speedometer repair is not a DIY proposition .
Back in the day , speedometer shops were in every good sized town . With the advent of electronic speedometers , most went away .
The best place to look for a speedometer shop is in some place like Hemmings Motor News .

 

Thank you
I was hoping this was something I could do myself
but I guess I'll need to see if I can find a shop to do the work.
Does anyone have a suggestion for a shop in the Chicago area?

 

Mine's got the opposite problem, it reads 4 MPH low at all speeds. This is a "zero offset" error in the speedo's calibration. There might be a staked factory adjustment that was not intended to be used later, or it might not be adjustable at all. One thing that can be done is to remove the needle from the shaft and replace it so that is properly points at "0", but this would require near complete disassembly of the unit.