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4:10's or 3:73's in an a4

This is a discussion on 4:10's or 3:73's in an a4 within the Drivetrain forums, part of the LSx Technical Help Section category; I might be selling my 4.11 gear in the Moser 9" after I get my Procharger installed....

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    Moderator 35th-ANV-SS's Avatar
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    I might be selling my 4.11 gear in the Moser 9" after I get my Procharger installed.

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    Quote Originally Posted by shady milkman View Post
    basically he is saying why make a huge deal out of it..debating about gas mileage and other shit instead of manning up



    Quote Originally Posted by 35th-ANV-SS View Post
    I might be selling my 4.11 gear in the Moser 9" after I get my Procharger installed.

    Very cool. This is a great example where alot of rear gear wouldn't be necessary. Something along the lines of a 3.70 or less would work nicely depending on the end goal.....

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    Quote Originally Posted by shady milkman View Post
    basically he is saying why make a huge deal out of it..debating about gas mileage and other shit instead of manning up
    calling me out eh? lol no i see where you are coming from

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    Quote Originally Posted by Firebirdjones View Post


    Very cool. This is a great example where alot of rear gear wouldn't be necessary. Something along the lines of a 3.70 or less would work nicely depending on the end goal.....
    Yeah. I originally did not put the 3.73 gear in it because I knew I would not be going FI for a few years and I still wanted to be able to enjoy some off the line acceleration. Obviously going this route probably is going to cost me a few hundred more, but it was worth it

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    here's a graphic going back to the 60s' & 70s'



    having a wicked gear helped in making sure you brought enough.

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    Quote Originally Posted by oldmanZ28 View Post
    here's a graphic going back to the 60s' & 70s'

    Click for full size

    having a wicked gear helped in making sure you brought enough.

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    Retired NOT tired SteveC's Avatar
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    Quote Originally Posted by Firebirdjones View Post
    2800 @ 80 mph is more than acceptable. Thats speeding just about anywhere you go, even here in AZ where the limit is 75.
    You could tame the cruise rpm down quite a bit and still be within what I call an acceptable cruising speed (65-70ish), and still get decent mileage if you wanted.

    It's why I've always said, "when you have an overdrive, why contemplate the rear gear change?"
    I am running 285x35x18, and turning 2800 rpm with my 3.73's @80mph, he must be running a very high tire getting that rpm with 4.30's

    SteveC

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    using
    http://www.f-body.org/gears/
    gives the following data for

    235/35/18(25.9" tire dia.) w/3.73s' @ 80mph=2700 rpm
    2800 rpm @ 80mph w/4.30s'=29" tire dia.

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    TunedByFrost supporter rel3rd's Avatar
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    Quote Originally Posted by BrianH.WS6 View Post
    from personal observation, 3.42's w/a 3200 stall is just about perfect for a bolt on-stock car in the 1/4 mile. you will still get anywhere between 19-21mpg on the highway around 75mph at 2400 RPM's

    If you have a H/C car you will want the 3600 stall. On an auto that cruises frequently on the highway @ 70-80mph you don't really want to go higher than 3.42's If you still want to stay in or over 20mpg.
    I agree with BrianH. Since the original poster said he drives daily at 80mph, 410's will drain his pockets of cash much quicker than 342's. Been there, done that. 4anything with stock height tires sucks on the highway. GREAT for redlight to redlight, but in the real world, some people travel at highway speeds regularly...

    I put 342's in my old 2000 SS solely due to rear being broke when I bought the car. (stock was 323's). I also swapped in baby cam (226/226), and Precision Industries Vigilante 3600 stall. Car still got 20+mpg's in high speed highway cruising.

    EVERYONE said I needed more gear to run quicker than my normal, and VERY CONSISTENT 11.60's at 116. Sixty foots were regularly 1.60-1.62's all day long, ANYWHERE. Best 60' of 1.57.
    I datalogged and kept records of any minor changes I made to setup, or tune, and literally made hundreds of runs in this car.

    I decided to try a set of 410's...

    Guess what?

    60 foots, ET's and MPH's were all damn near exactly what they were with the 342's.
    Best 410 geared ET was .02 quicker than my normal 342 geared runs.
    Best 410 geared MPH was exactly the same as average 342 geared runs. (116)
    Best 410 geared sixty foot was exactly the same as average 342 geared runs. (1.61)
    MPG's with 410's was 15mpgs driving at 65-70mph normal highway cruising, compared to 20+ at same speeds with 342's...

    Needless to say, I swapped back to 342's...it was a no-brainer.

    BTW, car yanked the driver's wheel on damn near every single footbrake launch I ever did (with the 342's and 99% stock suspension)...

    Click for full sizeClick for full sizeClick for full size

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    I agree with most of above,except for bad gas mileage,maybe mine was an exception to the norm. with the OEM 3.23s' I got 24.5mpg on 7 trips to Florida from Cleveland at freeway legal speeds. with the 4.56s' I got 21.5mpg on 3 identical trips. the ScanGaugeII showed a drop in 'engine load' parameter. As engine load goes down,the computor will lessen 'richness'(but still within factory operating specs) and mileage did not drop as much as it should have.
    Currently running a TCI 2800,when I swap in a different trans(trans in car has a broken forward sprag),I'll be putting in a Yank SS3600 and then going to either 3.73s' or 3.42s'.
    Probably the 7.625 3.42s' instead of the 7.5 3.73s' because the OEM gears,I consider,to be stronger.
    Gears can make up for a 'lack of stall' but with a good hitting higher stall,you don't need a wicked gear.

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    Moderator Firebirdjones's Avatar
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    Quote Originally Posted by SteveC View Post
    I am running 285x35x18, and turning 2800 rpm with my 3.73's @80mph, he must be running a very high tire getting that rpm with 4.30's

    SteveC
    Using the tire size you have given, you tire is only 25.85 inches tall. That's pretty short by most standards and that's why you are turning more rpm.

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    Quote Originally Posted by rel3rd View Post
    I agree with BrianH. Since the original poster said he drives daily at 80mph, 410's will drain his pockets of cash much quicker than 342's. Been there, done that. 4anything with stock height tires sucks on the highway. GREAT for redlight to redlight, but in the real world, some people travel at highway speeds regularly...

    I put 342's in my old 2000 SS solely due to rear being broke when I bought the car. (stock was 323's). I also swapped in baby cam (226/226), and Precision Industries Vigilante 3600 stall. Car still got 20+mpg's in high speed highway cruising.

    EVERYONE said I needed more gear to run quicker than my normal, and VERY CONSISTENT 11.60's at 116. Sixty foots were regularly 1.60-1.62's all day long, ANYWHERE. Best 60' of 1.57.
    I datalogged and kept records of any minor changes I made to setup, or tune, and literally made hundreds of runs in this car.

    I decided to try a set of 410's...

    Guess what?

    60 foots, ET's and MPH's were all damn near exactly what they were with the 342's.
    Best 410 geared ET was .02 quicker than my normal 342 geared runs.
    Best 410 geared MPH was exactly the same as average 342 geared runs. (116)
    Best 410 geared sixty foot was exactly the same as average 342 geared runs. (1.61)
    MPG's with 410's was 15mpgs driving at 65-70mph normal highway cruising, compared to 20+ at same speeds with 342's...

    Needless to say, I swapped back to 342's...it was a no-brainer.

    BTW, car yanked the driver's wheel on damn near every single footbrake launch I ever did (with the 342's and 99% stock suspension)...

    Click for full sizeClick for full sizeClick for full size

    .

    .
    It's all a matter of where your car makes power You are one of the few on here that isn't afraid to experiment. And that's what needs to be done to find the best combo for any particular car.

  13. #93
    Retired NOT tired SteveC's Avatar
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    Quote Originally Posted by oldmanZ28 View Post
    using
    http://www.f-body.org/gears/
    gives the following data for

    235/35/18(25.9" tire dia.) w/3.73s' @ 80mph=2700 rpm
    2800 rpm @ 80mph w/4.30s'=29" tire dia.
    You are correct on the first analogy (3.73's) however using fbody.org setting the same tire parameter using "1998 fbody a4" and 4.30 ratio, you were going 72mph @ 2800 rpm.

    SteveC

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    Moderator Firebirdjones's Avatar
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    I still find that very acceptable. 72 mph is plenty fast for me to get where I am going, and 2800 rpm isn't too much to ask for a steady cruise rpm. Actually it's right where I like to put most of my cars and I still find pretty good mileage on the old classic cars by doing that.

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    I used that calculator to tell me what size tire an 98A4 w/4.30s would need to run 80mph @ 2800 and it showed 29"

    I didn't plug in a 'same tire Dia',I wanted it to tell me tire Dia.

    If you allow 1000rpm as the typical low end operating rpm and 6000rpm as the typical high end operating rpm,the middle of that range(6000-1000=5000 divided by 2=2500),1000 + 2500 =3500,6000-2500 =3500,3500 is the middle of the designed operating range,2800 is still not up to the middle of the designed rpm operating range.That's why I'm never concerned about spinning the engine w/4.56s'.
    Last edited by oldmanZ28; 11-22-2010 at 08:29 AM.

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    TunedByFrost supporter rel3rd's Avatar
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    Quote Originally Posted by Firebirdjones View Post
    It's all a matter of where your car makes power You are one of the few on here that isn't afraid to experiment. And that's what needs to be done to find the best combo for any particular car.
    Agree 100%

    Heck, most everyone says a car has got to be quicker/faster with a cutout...Mine was louder, and that was it. lol. Same ET/MPH as through a dual/dual catback...go figure.

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    Quote Originally Posted by rel3rd View Post
    Agree 100%

    Heck, most everyone says a car has got to be quicker/faster with a cutout...Mine was louder, and that was it. lol. Same ET/MPH as through a dual/dual catback...go figure.
    I found the same thing with a cutout on the single catbacks. I've even found similar results on two other cars that have a dual cutout setup on them.
    It's good to see you on here again.

  18. #98
    TunedByFrost supporter rel3rd's Avatar
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    Quote Originally Posted by Firebirdjones View Post
    I found the same thing with a cutout on the single catbacks. I've even found similar results on two other cars that have a dual cutout setup on them.
    It's good to see you on here again.
    Thanks. I actually lurk here almost everyday....just usually spectating, lol

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    Firebird....or anyone else for that matter.

    Do you think with my stock cam/heads and that 4.11 gear it's going to be a total waste with FI? I do plan on going with a higher gear...just didn't know if I should do it immediately or not.

    My guess is I'll be blowing the tires off the car and going through gears like crazy!

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    some testing/experimenting
    stock horsepower-no engine mods stock 3.23 gearing
    2.02-60 low 13.70s ET 100mph
    same except for TCI 2800 convertor
    2.02-60 low 13.70s ET 99mph lost mph due to convertor looseness?
    TCI 2800 4.56 gears
    1.92-60 mid 13.20s ET 103mph M/Ts' 275
    1.86-60 mid 13.20s ET 102mph Nitto 315s'

    figures are not of just one run,but averages of many runs and at 2 different strips(same results at either strip),Thompson-NE Ohio and Norwalk/Summit

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