66 Chevelle SS396 & 66 Chevelle 327 Convertible.
Have a old Kneeknocker tack in my 66 chevelle. It reads about 3300 when it should read 2800 when traveling at 60 mph with a 3.55 rear end with a tire diameter of 26.1" Verified the speed with two other cars whoes speedometers are correct. Mine is wrong pretty sure the speedometer gear is for a 3:31 rear end, so my speedometer reads at about 67mph. Question is there any way to recalibrate the tack? Thanks, Jim