Let's say you pull the rear end and have a pro pull out the 3.27 gears and drop in some new 3.73s, then install the axle back into the car. From that point, exactly what else is involved to get the car to function perfectly in terms of computer calibration, auto tranny shift points, speedometer, etc? When going from a 3.27 to a 3.73 on a late model, is it possible to just swap a speedo drive gear in the tranny, or must speedo calibration be taken care of via a computer alteration? Etc. I'd really appreciate it if someone could point me to any articles out there on this subject, or perhaps account from your own experiences. I have done a lot of searching and have still not yet found a truly all-inclusive article about how to do a complete rear gear swap on a late model. It seems that pulling the rear and having a pro shop swap in gears is the easy part... I am mostly concerned about what else needs to be done to the car to get it to run and operate perfectly from that point forward. Having an auto tranny throws an extra monkey wrench into things, as there will most likely be an issue with shift points. I know when I swapped rear gears on an old auto tranny Firebird I had back in `77 (went from a 2.41 to a 3.23), the shift points then occurred way too early, since the shift points were partly governed by rpm. I merely altered the mechanical weights and springs in the tranny that were responsible for the shift points, and got the tranny to shift at perfect points... nice and easy before the days of computers. I am fearing that once I'd swap in a
3.73 rear in my late model Stang, that I may have some serious headaches getting the tranny calibrated right etc... or maybe not...??? Hope I can find some good info on this. Thanks!I have come to the conclusion that the two best mods for me are a rear gear swap to 3.73, and the Steeda ignition timing advance kit. These two mods should help give the car more streetable low-end kick without compromising anything (except for maybe a little fuel mileage). I am not really worried about increasing upper-end horsepower since I do not drag race for competition, I just want the car to be more fun to drive around on the street... seems I spend most of my time in the 2000-3500 rpm range. My goal is to really increase low-mid range available torque so the car has more kick where I use it... I think the rear gears and a bump in the timing would do the trick.