3.55 vs. 3.73
 

I have a 91GT Conv. So far I have done American Thunder Flows, MAC H-pipe, K&N Filter/AirSilencer Removed.
For my next mod, I will be installing a new gear ratio. My car is an AOD, and I want to know which would be better overall, 3.55 or 3.73? I drive on the highway at times, but not really a lot. I know that 3.73's are better perforance wise, but would they be overkill for a daily driver? Would would you guys recommend?

Also I have a MAC h-pipe w/ hi-flow cats, and 2 chamber flows, which is not a bad set up. The car is loud, but not too loud, compared to other stangs that have off-roads. Should I get an Off-road or keep it the way it is? If I got equal legth headers, would my car be a lot louder? Thanks

With the AOD, I would get the 3.73's - maybe even 4.10's. 3.55's with an AOD wouldn't be worth it in my opinion.

You'll be fine with a daily driver and 3.73's or the 4.10's.

Good luck with your decision.
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Gears and mileage
 

3.73 is the way to go with the AOD transmission.

The highway RPM's will be well within the 2000 range and gas mileage will hardly be affected.

The myth of poor gas mileage with a numerically steeper rear gear is way, way overblown and shouldn't even be a factor in your decision.

With that more realistic attitude toward the effects of gears on your mileage, think about 4.10's.

Considering you have a heavy vert auto I would go with 4.10's.

People say

4.10's for auto
3.73's for 5 speed

Later,

While we're talking 4.10s... I need to get gears for my automatic as well... I do alot of highway driving... to and from work, only about 10 miles each way though, and visit my parents from time to time on long island, and that's like 250 miles each way from boston... i dont mind the revs if the engine wont... and gas is a slight consideration... what kinda difference in gas and revs are we talkign here.. I mean I can do that math... but from a practical sense.. does anyone run 4.10s and do considerable highway driving... does it SUCK is it OK? the overdrive aspect certainly helps.. I've got a 72 Olds with 3.42s and it's only a 3 speed auto and it does about 3500RPM when I'm crusing at about 80... and I can live with that.. it's alot louder then the mustang too for that matter..


-as

4.10's on auto and 3.73 on manual.......unless you plan on running a big SC or turbo set up, then you may want to stick w/ 3.55's on the manual and 3/73 on the auto. Just my .02

Gears
 

TwiLitghTbluEGT:

On an AOD with 4.10 gears you're probably looking at about 2400 RPM at 60 mph. Just a ballpark guess but probably close and as you can see, no problem. 3.73's would probably be around 2200 RPM or less.

With stock size tires and a .67 overdrive ratio(I'm pretty sure that's what a AOD's is) you will turn these RPMs at 65mph......

3.55----2029rpm
3.73----2132rpm
4.11----2349rpm

For performance I would go with the 4.11's

tireburner163......that "altezza's are gay" mpg is hilarious. LMFAO :D