There seem to be lots of 4x4 aod trannys coming up for sale in my area. I've also read that they were the strongest from the factory. I'm looking to put one in a 80 cobra that has a carb'd roller cam motor. (anyone need a 255?) Do you just need to swap out the tail shaft adapter? I know i need a tv cable and brackets. The C4 in the mustang works fine, just looking for better gas mileage.

it's next to impossible. the physical casing will not allow you to simply swap out the tailshaft for a 2WD as the casings are 1 piece, you COULD remove the guts change the ouput shafts and put them into a 2WD AOD housing. 4X4 AOD's will always need a transfercase of some sorts bolted to them. Besides as a 4X4 guy myself AOD's are the biggest POS tranny built (there's a reason you see LOTS of AOD 4X4 trannies for Sale. Its because everyone is either upgrading to the much MUCH stronger C6 or E4OD as they are tired of the POS AOD failing them constantly. You would be better off swapping in a 5-speed manual.

I agree with Keith C. The amount of labour required to "modify" a 4X4 AOD transmission, which would consist of disassembling the transmission completely, and replacing the output shaft with one that is used for 2WD applications and the tailshaft housing alone, will make it cost prohibitive. There is also another weak link on the AOD, and that's the two-piece input shaft. As Keith C says, you are better off swapping in a good T-5, or Tremec 5-speed, if better fuel economy is that much of a priority.