How to fix my speedometer

Question

i have a 99 mustang gt and i just recently put 4.10 gears in it and since the installation of my gears my speedometer is off by a bit but i not sure exactly how muh but i know its atleast 15mh anyone have any ideas on what i can do to fix the problem

Answer 1

If you know Your speedo gear tooth count than use the following formula.



Old Tire Diamater / New Tire Diameter x  New Gear Ratio/ Old Gear Ratio x Old tooth Count = New spedo gear needed

If you dont know your factory speedo gear tooth count here is a formula

(63360/(MSODx3.14159)xAxle Ratio) / 74.5

   = # of teeth in spedo gear.

Answer 2

HI

First off. Disregard the other answers as they are all WRONG!!!

i have calibrated many of those vehicles.

the Speedometer is an analog display ( not digital ) but is still run using an electrical sender. There is NO gear to change on this year mustang!!

The speedometer must be removed. Inside the instrument cluster you will see one or two potentiometers. Just turn the pots clockwise to speed up speedo/odo or turn counter to reduce speedo/odo.

it is that simple.

I would charge a customer $100 to do the whole job. This includes verifying the inaccuracy and removal and calibration and rechecking and final installation!

No...doing this calibration will NOT change the odometer reading. It will just make the speedo/odo more accurate.

I hope this helps!

Answer 3

Change the speedo gear in the tranny. A speed shop will know which one you need.