Slowmotion559

Does anybody no roughly if there is some kind of calculation to figure this out? The car is a 2001 Coupe with an auto. Looking for a set of gears to help at the dragstrip but still be daily driveable and get decent gas mileage. Right now getting over 20 mpg just wondering if switch gears to the ones listed will reduce mpg drasticly.

ohchiiit

my car has 3.15s and still gets 28mpgs! ive also thought about 3.42s and would be curious what the difference would be.

4DRUSH

Way I see it, all depends on saving a couple hundred bucks on gas or having more fun with your car before you sell it or die.

obnoxus

Not enough to talk about,,,,,,

QCVette

Your in town mileage will not change to much since it is more dependent on how hard you use the pedal to get up to speed.

Your highway mileage will be a little worse. You may be able to approximate it by doing some calculations and a trial. Your 3.15 axle in 4th gear has an overall ratio of 2.205 (3.15 x 0.70). In 3rd gear it has an overall ratio of 3.15 (3.15 x 1). A 3.73 in 4th would be 2.611 and a 3.42 would be 2.394.

To use these numbers try a test and compare your highway cruise mpg in 4th gear. Try it again in 3rd gear. Remember the amount of change. If you go to 3.73 axle it is a little less than half of the difference between 3rd and 4th. If you go to a 3.42 axle it is a little less than a quarter of the difference.

For example, if you now get about 28 mpg and in 3rd you get 24 mpg, then with a 3.73 you would get about 26 mpg, or 3.42 about 27 mpg. These numbers are only a guess (you would need to try 3rd and 4th gear mpg tests) and this method is only a ball park guess, but might be close enough for you to tell if you can live with it.

Good luck.

RonSSNova

I have 3.42 in my 2000 A4.
Car runs bottom 11's with a best of 10.99.
By the DIC, I get 25-26 on the highway.
Around town is all over the map depending on traffic.

Ron

Rob Petyo

Who gives a chit really ... I went from 2:72 - 3:42 - 3:73 and the mileage isn't too bad but I like to play with it too much and avg about 10. Also have a 4k stall, it spends a LOT more time revving ...

I can get about 22 @ 65 mph cruzn

StrangelovesM6Vert

If you are ok with 2800 rpm at 80 mph go with the 3.73
The 3.42 will be about 2400 rpm at 80 mph.
I had both 3.42 and 3.73 in my 97 A4 Camaro and 3.73 was more fun but the car felt like it needed a 5th gear on the interstate.

kh400

I went from 2:73 to 3:42 gears plus a 3000 stall convertor with a lockup feature. If you go to the trouble of gears, make sure you go with a higher stall convertor. I would say i I lost 2-4 mpg. But the car is a beast now. Good luck!!!

Rob Petyo

I'm gonna have to try to remember where my tack is at @ 80 mph, I think it's higher then 2800 and get back.

At 80 with a built motor going down the interstate, it doesn't feel like it needs anything - it's now running with the BIG Dawgs - and the power is in my range for a nice little roll. my cars will smoke tire at 80 ... I've driven from NJ to FL a few times with gears and I loved the ride - just saying - also I don't think I would ever go back to 3:42's, they are boring

bjones7131

I have a 3.42 M6 and on a recent 140 mile trip I got 30.4 MPG per the DIC.

Rob Petyo

If you drive like there is an eggshell between your foot and the gas peddle, you could probably get better mileage.

I'm not sure how that relates to an automatic

bjones7131

Doesn't relate to an automatic but giving info for OP comparison only and I needed the typing practice on keyboard. Have a big day