How to Calibrate a Speedometerby Contributor
You may figure out the hard way that it's time to calibrate your speedometer. It could be that you got a traffic ticket for speeding and you know that your speedometer was registering the speed limit. Maybe you're continuously honked at for driving too slow when again, your speedometer registers the speed limit. Either way, you need to calibrate it. Follow these steps to properly calibrate a speedometer by yourself.
Determine how far off your speedometer is. You can do this by driving past one of the speed radars that many highway patrols place on the side of the road. Notice the reading on the radar and on your speedometer and calculate the difference.
Call the dealership or an auto parts store and let them know what gear you currently have on your speedometer and how far off your speedometer reading is. You can find information on your speedometer gear in your auto manual.
Gather your new gear, a cloth, an 11 mm wrench and needle nose pliers. Remove the speedometer from the car. Wipe it off with the cloth as it may be covered with automatic transmission fluid.
Use the pliers to take off the retaining clip. Remove the gear from the speedometer assembly.
Install the new gear into the speedometer assembly. Put the retaining clip back on.
Place the speedometer assembly into the tail shaft again and secure it by tightening the bolt. Line the gear up with the speedometer cable.
Test your speedometer again to see if works correctly. If not, you may have had an addition or subtraction error in figuring out the difference in speed. Return the gear to the auto parts store and get the correct one.