I've been looking more into the idea of swapping in some 3.73s in place of the 3.27s.
According to my calculations on paper, if the engine is to be shifted at
5,500 rpm, with a 3.27 rear, the 1-2 shift occurs at about 44 mph, 2-3 shift at 81 mph, and 3-4 shift at 125. However, with a 3.73 rear, the 1-2 shift would occur at 39 mph, 2-3 shift at 71 mph, and 3-4 shift at 110 mph. From this you can see that the 3.73 rear allows peak hp to occur earlier (of course), and specifically help 0-60 mph times, and 1/4 times given the tranny ratios. It puts more average hp under the 0-60 mph run and 1/4 mile run (while not adding an extra shift point to either run.). Also, in terms of highway cruising, with the 3.27 rear, the engine should spin at around 2154 at 70 mph, while the 3.73 rear would make for 2457 rpm, just 300 more rpm. Not too bad. A change any smaller than this would not be worth the effort and expense of the gear swap... so anyone looking to try a 3.55, it's not worth it unless someone gives you a free Mach 1 rear. Going up past a 3.73 to a 4.11 would make for more useable street power, might even be perfect for best possible 0-60 and 1/4 mile times, but then the cruising revs start to climb up a bit higher than "optimum". 3.73's seem to be the perfect compromise between max street performance and good economy / high-speed cruising behavior.Once again... does anyone know of a Mustang specialty shop anywhere in the north east that can be trusted to do a rear gear swap? I'd never let any clowns touch a rear axle unless they had a stellar reputation. So far I've read about a dozen stories on the web from guys who had their gears swapped only to result in failures and problems... have not yet heard one gear swap success story, at least not for the late model Stang. I had a highly experienced ace race mechanic rebuild my old Trans Am posi rear, and he did a perfect job, but that was 12 years ago... not sure if I can find that guy anymore, or if he is as swift with Fords as he is with GMs. I'll gladly pay top dollar to any super ace Ford mechanic or rear-end mechanic that has a flawless rep for doing such work on these rears. If anyone knows of such a person or shop, please post. Thanks.