[duplox]

I think the c4 is shorter than AOD, so you will most likely need a new driveshaft. You'll need a new shifter. And yes, it has 3 gears, so it will only shift twice(1 to 2, 2 to 3...). The AOD was ford's first auto with more than 3 gears. The GM powerglide is a two speed auto. C6 is a 3 speed also, but much beefier than the c4. The c4 does not have overdrive, so you will have a lower top speed, if everything else is the same. Cruise RPMs on the highway will most likely be higher, unless you normally cruise in 3rd gear with the AOD.