^^^ Yep. If your only getting 10-12 mpg with AOD and 2.73'sI think you have other issues you may wanna look at or buy a gas saving car to were out

 

Depends on the ratio of the overdrive gear. The reason the 4.10's get the bad rap about mileage is because the RPM's are higher at cruising speed. Naturally that will burn more gas. Therefor is you have a higher ratio overdrive ie .60:1 which is the common ratio on the 6th gear of the F-Bodies t56 if Im doing my research properly, as opposed to the .78:1 5th gear ratio of a t5 on the mustang. The 6th gear will offset the extra RPM's caused by the 4.10's.

As for city driving, my friend had a 97 GT that he only drove around in town. When he went from the stock gears to the 3.73's he actually got "better" gas mileage. Lower gears give a car more mechanical advantage and the engine doesnt have to work as hard so you dont have to rev as much to get moving.

 

A cheaper option would be to find a T5 with a good overdrive. Mine has a .62 fifth gear. You can decipher a Borg Warner tranny tag here: Identification Key to Borg-Warner T5 transmission ID Tags

Just my .02

 

^ill look into that also.. the reason im getting horrible gas is b/c in town its boggin at 1500 rpm every where and working really hard. i actually think once i put the 4.10s in i might get better milage intown with the aod due to it being out of the bogg zone lol

 

thats what i was thinkin, even though the cars are not known for good MPG, there not that bad, even street driven carb'd ones.