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373 gears on a4 and gas mileage

This is a discussion on 373 gears on a4 and gas mileage within the Drivetrain forums, part of the LSx Technical Help Section category; have a 2002 z28 and would like to change to 373 for some extra acc but a little worried about ...

  1. #1
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    373 gears on a4 and gas mileage

    have a 2002 z28 and would like to change to 373 for some extra acc but a little worried about gas mileage over 60 mph and extra wear on the tranny. Will the switch to 373 give me a noticible gain over the stock. Also have slp bellow lid and ram air and a catback

  2. #2
    Junior Member WS6 > SS's Avatar
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    I too am curious! I was even considering going with 4.10's just to get the maximum out of my gears.

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    i wanna know too! also if its worth the performance gain.

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    Exalted Cyclops 67CamaroRSSS's Avatar
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    2002 Z28 A4 NBM
    Sadly now demodded :(

    While I have considerably more than just gears done to my 02, 3.73 gears were one of the 1st mods. Originally my car had 2.73's so it was a real big improvement in acceleration with very little loss in driving. I lost a goodish bit on the top end (where can you drive 150mph anyway?) but it was only a 5-600 rpm difference at 65 mph.

    3.73 vs 4.10 final drive (for a daily driver) is best determined by which tranny you have. An M6 (due to the .5:1 OD in 6th) works better with a 4.10 and an A4 (.68? OD in 4th) works better with a 3.73.

    Do either of you know which gears you have and what type tranny? Look on the door sticker if it's still there. IIRC, GU2 = 2.73, GU5 = 3.23 (these were used on A4 trannys) and GU6 = 3.42 (used with the M6).

    1st thing you gotta figure out is: What do I want to do with the car? I bought the 98 to DD and modded the 02 to drag race.
    Last edited by 67CamaroRSSS; 02-12-2010 at 03:20 PM. Reason: clarified gearing

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    Member jetaws6's Avatar
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    4.10s in an automatic 4 will destroy your gas mileage for highway driving 3.73s would be the most I would go in an a4. I dont have gears in my car but my friend upgraded from 3.23's to 3.73s in his m5 mustang gt and shaved off three tenths in his 1/4.

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    ya i have the 3.23s

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    Just upgraded from 3.23 to 3.73 gears in our A4 equipped car. Awaiting decent weather to try them out, but do not expect all that much difference in highway rpm. Mileage is not a concern with a car like this, but again the overall difference should not be all that great. The right foot is going to have more of an impact than the gears imo.

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    Senior Member tatertot91's Avatar
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    just put 3.73 in mine from 2.73s
    Don't know about highway, but its not much of a difference in the city
    will be able to get some highway #s later on
    Pretty big difference down low, 2nd pulls much better
    Haven't been able to get the pedal all the way down in first, car drives like its on a slip and slide

  9. #9
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    Gears do not cause extra wear on the tranny,actually just the opposite.The drivetrain(everything before the gears-engine,clutch or torque converter,and trans) now(with higher numerical ratio gears) has a better mechanical advantage over everything(weight of the car and fighting wind resistance) after the gears.
    MPG is mainly determined by your foot.
    My OEM 3.23s' on 6 trips to Florida from Ohio gave me 24.5mpg at freeway legal speeds,my current 4.56s' on 3 identical trips give me 21.5mpg.

  10. #10
    Retired NOT tired SteveC's Avatar
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    2001 Z28 (Sara)

    The difference between 3.23's and 3.73's is 500 RPM, a very minor difference in gas consumption.

    SteveC

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    Senior Member Z28_Driver's Avatar
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    The 3.23 gives me decent mileage on the highway. About 22mpg. A 3.73 shouldn't be much below that. My car has an A4 with some basic mods. Got 23mpg before the mods started and 24mpg before the trans rebuild.

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    12 SECOND CLUB FASTEDDIE Z's Avatar
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    Quote Originally Posted by tatertot91 View Post
    just put 3.73 in mine from 2.73s
    Pretty big difference down low, 2nd pulls much better
    Haven't been able to get the pedal all the way down in first, car drives like its on a slip and slide
    LOL ! You too ? When I went from 273's to 373's I was happy and disappointed at the same time . I was happy how much quicker it felt ,but disappointed I couldnt get any traction at all in 1st gear and sideways all the time when it shifted 2nd . Now I have 315 35 17 nitto D/R's and Im use to them . So I bought a Yank 4000ss tq. converter . If I did it again I would of done 342's .I miss my 273's on the hwy.

  13. #13
    Senior Member tatertot91's Avatar
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    Sunset Orange Metalic
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    Quote Originally Posted by FASTEDDIE Z View Post
    LOL ! You too ? When I went from 273's to 373's I was happy and disappointed at the same time . I was happy how much quicker it felt ,but disappointed I couldnt get any traction at all in 1st gear and sideways all the time when it shifted 2nd . Now I have 315 35 17 nitto D/R's and Im use to them . So I bought a Yank 4000ss tq. converter . If I did it again I would of done 342's .I miss my 273's on the hwy.
    Yeah, kinda miss my old traction
    My cars almost never on the highway so its not too big a sacrifice.
    now i need a stall and some DRs and i'll be good to go

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    i have 373 and a 3400 stall with cat back(slp loud mouth) air lid tuned and i get about 18 to 19 mpg if i drive like a normal person,but the worst i have ever got is 16 or so but that was with a lot of hot roddin in town

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    Retired NOT tired SteveC's Avatar
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    Quote Originally Posted by heath26 View Post
    i have 373 and a 3400 stall with cat back(slp loud mouth) air lid tuned and i get about 18 to 19 mpg if i drive like a normal person,but the worst i have ever got is 16 or so but that was with a lot of hot roddin in town
    Your low gas milage is due to the converter ineffeciency.

    SteveC

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    Junior Member Glue Maker's Avatar
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    i ride 50/50 street highway would yall do 3.73 or 3.42?? im running a yank 3600 with 2.73 and am having traction issues already lol

  17. #17
    Senior Member tatertot91's Avatar
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    Quote Originally Posted by Glue Maker View Post
    i ride 50/50 street highway would yall do 3.73 or 3.42?? im running a yank 3600 with 2.73 and am having traction issues already lol
    I love my 3.73s on the street but hate looking at those rpms when i hit the highway and i'm barely on the highway. I would go 3.42s if i was on the highway more.

  18. #18
    Retired NOT tired SteveC's Avatar
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    Quote Originally Posted by Glue Maker View Post
    i ride 50/50 street highway would yall do 3.73 or 3.42?? im running a yank 3600 with 2.73 and am having traction issues already lol
    I would go with the 3.73's.

    SteveC

  19. #19
    JMAC Racing WS6ICK's Avatar
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    2000 Trans Am WS6 LS6
    2006 GTO LS2

    A4= 3.73
    M6= 4.10

    If your worried about gas mileage, get a V-6.
    2010 Camaro
    2006 GTO, LS2, 1 of 475
    2009 Chevy Silverado


  20. #20
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    Quote Originally Posted by WS6ICK View Post
    A4= 3.73
    M6= 4.10

    If your worried about gas mileage, get a V-6.
    right on

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