Dan04COBRA

Here is a link to the Richmond Gear calculator http://www.richmondgear.com/101032.html

Gears, without a doubt seem to be the most commonly asked question throughout all of the tech forums here at MF. A lot of bad info has been spewed forth and unfortunately people are buying into it. This is my own take on selecting gears for any given car.
First lets all get on the same page. Low gears are numerically high i.e. a 4.30 is a LOW gear, conversely a 2.73 is a HIGH gear. This may be basic but I think there are people who don't get this, remember we are talking about a ratio like 2:1 for example.
The most important thing is to honestly ask yourself what kind of goals you have in mind, if going fast your #1 priority then it's pretty easy, get a big gear and a big tire. If you want all around good performance I like 4.10's Personally I don't think anything less than a 4.10 is even worth swapping in, UNLESS you have a C4 or C6, with our modern over drive transmissions we can have our cake and eat it, so to speak.
Second is you need to look at your car as a whole system, in other words if you just put in a big cam and make power into the 6500+ rpm range then a 3.73 is not going to cut it. Even if you don't race a car like this just driving it around will be a chore. Big cams tend to shift power higher into the rpm range and with a high (numerically low) gear you will be lugging the engine a lot.
There also seems to be a trend that supercharged cars need higher gears (3.73' come to mind) and while you might want them because of fuel economy and such, the fact is that if the engine can rev high enough and you can get traction, the car will go faster with a lower gear, it is basic physics. The lower gear allows for more torque multiplication and thus a faster rate of acceleration.
One other thing to remember is that tire height affects the overall gear ratio as well. For example going from a 26 inch tall tire to a 28 will raise the ratio (it makes your 4.10 "feel" like a 3.73). So pick a gear with your tire size in mind.
There will always be cars that like a different gear than what conventional wisdom calls for but for 99% of the members here who have a car with overdrive (AOD or 5 speed) a 4.10 is really a great gear choice. If you type in "gear calculator" into google you will find a bunch of programs that allow you plug in you tire height and gear ratio to find out your mph is at a given rpm. Most times it will be about a 200 rpm difference at a given speed to go from 3.73's to 4.10's, that’s it 200 rpm is not much of an rpm difference but the advantage of the 4.10 is a lot.

TimmyGt

The calculater says that with the 4.10 my gt would be running at 3,709 rpm @ 70 mph. that sounds really high! did I do it wrong or will it be that high?right now Im only running @ about 2,000 rpm

Car_Ramrod

personally i like this calculator better...


http://www.tchracing.com/tech/gearca...selectedgear=5


it says with 4.10s you would be turning like 2500 rpms in 5th gear with a 5-speed in a 97 GT with a T-45.

TimmyGt

that one works great. it sounds a little better