i bought a used 1989 mustang gt automatic with a aod tranny and would like to know how do i tell if i have rear end gears with out taking off the diff cover off and counting the teeth on the ring and pinion. i was also have another problem when iam slowing down from a cruise at about 50 mph i get like a binding or dragging like feeling on the slow down what is this to my knowledge the tranny is stock with no shift kit and it has the stock converter

 

You have gears in the rear end for sure. If you want to find the ratio....................
Block the front wheels, jack the rear end off the ground, use chalk or tape to marka spot on thedrive shaft and tires, bottom works best.Rotate the shaft and countthe rotations untilthe mark on the tire come back to the original position.


Edit: Forgot to mention make sure car is in neutral

 

if the drive shaft goes around 4 times to the tires 1 then you have 4.10, if it goes 3&3/4 then it's 3.73, goes 3 1/2 then3.55, goes 3 then 3.08 which is stock on most of your 5 speeds

 

i was also told if i put the car in drive and crusie at 70 mph and the rpms are at 3,500 i have 355s, if its at 3,700-3,800 i have 373s, do you know if theirs any truth to that

 

That'snot an accurate way of determining gear ratio. Tire diameter will affect the rpms.Nothing wrong with removing the cover and changing the gear lube on an 89.The gear ratio will be stamped in the ring gear, no need to count teeth.

 

there are a few reasons why driving at a certain speed will tell you nothing

first off...when you do a gear swap, your speedo will be off...anything over 3.27 in an aod car and you cannot correct it...so you don't know how fast your really going to begin with

i can you right now....if your car needs it to be wet to spin your tires....you have 2.73 or 3.08 , if it breaks them loose then bogs then you have 3.27

look in your door tag...under "ax" it will have what your car came with

m=2.73, z=3.08 , e=3.27

the only way to know exactly is jack it up and count rotations....chalk the tire on the inside and ckalk the driveshaft too.

1 rotation of the tire completely...count the ds spins, then you'll have it