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Highest stock gear ratio in 9inch rears?

Discussion in 'The Hokey Ass Message Board' started by ford9inch, Oct 22, 2009.

  1. ford9inch
    Joined: Dec 26, 2007
    Posts: 100

    ford9inch
    Member

    What's the highest (numerically lowest) ratio put in 31 spline truck 9inches. I've got a 3.0 in my 9inch at the moment and don't really like it for highway cruisin. I've got what I believe to be a 2.20 something (?) in my 56 chevy truck with a gm 10bolt underneath it. Something similar to stab in my 9inch housing would definitely be sweet. Oh, and if anyone has anything close to what I'm looking for, I'll probably be interested in buying...if you're selling.
     
  2. i'm thinking maybe 2.56?
     
  3. i've been looking for a 2.79 (28 spline) but i'm not sure if they're made for 31 spline.
     
  4. KEITHMAN
    Joined: Apr 19, 2008
    Posts: 159

    KEITHMAN
    Member

    2.80's are the tallest 9" gear I know of. I'll check my books.
     
  5. CJ Steak
    Joined: Sep 23, 2008
    Posts: 1,377

    CJ Steak
    Member
    from Texas

    I had a 2.73 31 spline 9" with the SMALL 5x4.5 bolt pattern under my '82 F100 stepside pickup. It was a pretty wierd deal and part of an econo package I think. It got the light duty smogged out 300 with the aluminum SROD 4 speed OD out of the GT Mustang, and it came with the car bolt pattern front and rear from the factory.

    It was a dog... until I made that 300 scream. Economy went down the ****ter though lol.
     
  6. RichFox
    Joined: Dec 3, 2006
    Posts: 10,020

    RichFox
    Member Emeritus

    I run 2.47s in my Bonneville car. Common 70s big car smog gears.
     
  7. squirrel
    Joined: Sep 23, 2004
    Posts: 59,932

    squirrel
    Member

    2.47, 2.50, 2.75, are the high speed 9" gears
     
  8. ford9inch
    Joined: Dec 26, 2007
    Posts: 100

    ford9inch
    Member

    Well, sweet. Thanks for all of your input so far. I guess now what should be said is that I'm looking for a third member with 2.47s...for a 31 spline
     
  9. TomP64
    Joined: Dec 10, 2008
    Posts: 429

    TomP64
    Member
    from Vancouver

    I don't think there is any such thing stock, you'll have to combine a 31 spline carrier with the awful gears. You can find the 2.47's in late 70's Lincoln Versailles and full sized Lincolns but those are all 28 splines.
     
  10. JimSibley
    Joined: Jan 21, 2004
    Posts: 4,048

    JimSibley
    Member

    Why? Im not trying to be an ***. I am really wondering why you would want anything more than a 3.00 in a street car. I had 3.08s in my model A and it would cruize nicely at 75 mph.
     
  11. vendettaautofab
    Joined: Jan 9, 2006
    Posts: 1,602

    vendettaautofab
    Member Emeritus

    I have a set of 2.47 gears on the shelf, may not need
     
  12. George
    Joined: Jan 1, 2005
    Posts: 7,980

    George
    Member

    I had a '79 S/W with factory 2.25s:eek: Don't recall if 9" or not.
     
  13. Just Gary
    Joined: Oct 9, 2002
    Posts: 5,813

    Just Gary
    ALLIANCE MEMBER

    That was my initial thought. But maybe the tires are really short or the transmission's gears are less than optimized for highway driving.
     
  14. How tall are your tires?
     
  15. BigMikeC
    Joined: Apr 18, 2006
    Posts: 451

    BigMikeC
    Member

    I had a 2:75 9 3/8 in my 66' Galaxie with stock C6, 15in wheels. It would auto shift 2nd to 3rd gear with the pedal on the boards at 80mph. Top end... scary. But the bottom end was doggy with 428, 6barrels, mild cam, headers. With a 3:89 posi it would run 14.0's in the 1/4 mile. It's all about compromise. Whatcha guna do with it.
     
  16. Drive Em
    Joined: Aug 25, 2006
    Posts: 1,748

    Drive Em
    Member

    2.47's with 31 spline axles are common in the mid 70's big Lincoln 9" rear ends.
     
  17. shmoozo
    Joined: Aug 14, 2007
    Posts: 671

    shmoozo
    Member
    from Media, PA

    Just to put this in perspective, Currie Enterprises lists "good used 2.50 ratio ring and pinion" sets for the Ford 9" for about $100.

    Yeah, I expect you can do better than that if you are willing to do some legwork, but at least that gives you a starting point in terms of pricing.
     
  18. ford9inch
    Joined: Dec 26, 2007
    Posts: 100

    ford9inch
    Member

    I'm running 7.00 15s out back and a th350 for a trans. 3.0 isn't bad, I don't have a tach in the car right now but I know of friend's cars with 3.0 that turn around 3000 rpm at 70ish mph. The truck I was referring to earlier with what I believe to be around a 2.20something gear cruises around 2000 at 70mph, and I love it.
     
  19. squirrel
    Joined: Sep 23, 2004
    Posts: 59,932

    squirrel
    Member

    2.5 to 2.75 is a good place to be if you don't have overdrive, and you like going fast on the highway, and your engine has the torque to pull it. I've put a lot of miles on a set of 2.75 gears in my 55....having a mild blown big block makes the soggy bottom end not an issue. especially with the switch pitch torque converter.
     
  20. I don't think so...something is really not right there.

    I had 3.23's, and a very short 25" tall tire and was only about 3000rpm at 70mph. You are running a much taller tire, so you would be several hundred rpm lower.
     
  21. Shifty Shifterton
    Joined: Oct 1, 2006
    Posts: 4,964

    Shifty Shifterton
    Member

    Without trying to sidetrack the thread too far, what's the highest gear anyone's seen in a domestic rear axle? I always thought 2.20s were as high as they got but once bought a ten bolt out of a 79 police car.....the ****er had 2.13 gears! Yikes!
     
  22. squirrel
    Joined: Sep 23, 2004
    Posts: 59,932

    squirrel
    Member

    I think two teens is the lowest number I've seen. caddys had them before OD came along...late 70s was a great time for "high speed" rearend gears.
     
  23. ford9inch
    Joined: Dec 26, 2007
    Posts: 100

    ford9inch
    Member

    My truck has a camaro ten bolt not sure of the ratio (the only reason I ***umed they were around 2.20 because I had a 79 malibu with a ten bolt with a ratio around 2.20) with 235 75's in the rear and I turn around 2000rpm at 70ish mph. Been driving it for like 6 years now...been all over the country. I know what rpms that truck cruises and at what speeds.
     
  24. rainh8r
    Joined: Dec 30, 2005
    Posts: 792

    rainh8r
    Member

    The formula I use; DxRPM/Rx336
    D=tire diameter
    R=ratio

    This will give you the speed for your gears and tires. The numbers can be moved around to give all 3 variables.
     
  25. indyjps
    Joined: Feb 21, 2007
    Posts: 5,396

    indyjps
    Member

    check out some of the nascar used parts sites, better gears cheap
     
  26. Drive Em
    Joined: Aug 25, 2006
    Posts: 1,748

    Drive Em
    Member

    The used Nascar gears usually howl pretty good. They grind a crown in them for the optimum contact pattern, and they make some serious noise. I have bought several sets, and for race cars they are great, but they will drive you crazy on the street.
     
  27. Post Apocalyptic Kustoms
    Joined: Oct 21, 2012
    Posts: 479

    Post Apocalyptic Kustoms
    BANNED
    from Outside

    A few of us swapped one of those lincoln center sections 2.** range into a '58 Ford with a 352 interceptor and got in the 20's on MPG on the way to MOKAN one year. Not much good on the strip then, but the highway is what counts these days IMO.
     
  28. GearheadsQCE
    Joined: Mar 23, 2011
    Posts: 3,670

    GearheadsQCE
    Alliance Vendor

    You know what I would suggest!
     
  29. 302aod
    Joined: Dec 19, 2011
    Posts: 275

    302aod
    Member
    from Pelham,Tn.

    My 81 F150 came with 2:79 ratio 31 spline, 300 six and C6. I think the last year for the 9 in.
     

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