Hi, just want to ask whats the ratio of ring & pinion of stang 2003 gt v8 coupe? Thanks

 

If it's original & untouched there should be a steel tag attached to the cover with the ratio stamped on it. Lacking that you can jack up the rear and turn the wheels one full turn and count the number of times the driveshaft/pinion turns. For example if the pinion turns roughly three and a quarter times for one turn of the wheels you have a 3.27 rear gear. If the rear has a properly functioning limited slip you can turn either wheel. If it's an open diff have a friend turn one wheel while you turn the other and keep the rotation equal.