If your door tag remains intact on your 1986-95 Mustang GT or LX, there's a very easy way to find out what rear gears are in the car. When you open your driver's side door, you'll see a tag that looks like this:
The break down is simple. On the lower far right, you'll see a box that says "AX". Find the code in that box (it's a letter).
M = 2.73;1, which were standard equipment
Z = 3.08:1, which was a no charge option
E = 3.27:1, which was an option in the AOD/AOD-E cars.
So, if your door tag is intact, finding out which rear gears your Mustang was originally equipped with is a piece of cake.
