Eagle2000GT

Interesting comments from modern mustang. 3.73 gears are not really necessary. But they should go well with a centrifical supercharger. I might worry about them with a twin-screw but a centri is almost like driving a stock Mustang at low RPMs. At 2500 rpm I'm only running 1.8 lbs of boost. But the lower gear will allow me to get to the higher rpms faster where the centri really comes to life (mine generates 8.9 psi at 6000 rpms).

I've already ordered 3.73 gears and 31 spline differential/axles. They will be installed in two weeks. I was a little concerned that they might be too much gear for the number of miles that I drive on the interstate. But, if they are I have a fall back position. I'll put 255/50-ZR17 tires on the car and have the speedometer recalibrated. The larger tire will tone down the gear and make it approximately the same as 3.55s. These tires also will fill in the fender wells a little better. (Note: They have the same diameter as 245/45-18s but are cheaper.)

Armydad

Could you post after the swap and let us know if there is a noticable difference.

Eagle2000GT

I'll be glad to. The axles are suppose to arrive next week and it goes in the shop on March 9th. I'm really interested in what it will do to interstate gas mileage. Most people say 1-2 mpg less. But I want to test it and find out for sure.

MJH78

Well I can't say anything in regards to FI and 3.73's, but just with my mods listed below, having the 3.73s installed was very noticeable, definitely worth it. I mean it's not going to just completely transform the car, but it definitely makes every gear get into the powerband much sooner

IndustrialMechanic

I put 3.73s in my auto '01 and it made a noticeable difference. It'll break the A/S's loose easier than it did before and I dropped about .15sec in the
1/4. With the stock 3.27s it turned about 2K rpms at 67mph. Now it turns 2K rpms at 60mph and about 2400rpms at 70mph. Also, you can tell the engine isn't working as hard to get up to speed when your on it.

lgwilson

I went 4.10s after much debate about those or 3.73's and since I plan on staying NA I went the route I did. The gears will wake the car up tremendously. Best dollar for dollar upgrade I've done...by far. You should do the swap IMO.

Thanks to you and your family for serving our country. I know you must be a very proud dad.

Soldier GT

Very well said..

CubanoGT

Hmm I'm leaning towards 3.55

liljojo4711

are gears worth putting in an auto? how hard is the install? i drive about 65 miles on the highway about once every 2 weeks, would 4.10's not be a good choice? im staying n/a (car has 186,000 miles on it )...

mrtstang

I run 3.90's w/mods in sig, and i am on street tires as well. Several factors come into play when choosing the right gear. My recomendation would be to choose the steepest gear possible that will fit your personal needs while allowing a little room for growth. Some of us say "i'm keeping it n/a" only to find a great deal on nitrous or supercharger. That's why i chose the 3.90's. Something to consider...