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Customs Running 2.50 9inch gears.

Discussion in 'The Hokey Ass Message Board' started by DrewModelA, Aug 30, 2019.

  1. DrewModelA
    Joined: Oct 26, 2014
    Posts: 36

    DrewModelA
    Member

    I am installing a 2.50 ring and pinion in my Thunderbird. Anyone have any experience with a similar setup? I have the stock 352 4bbl with cruise o Matic. The car will mainly be a highway cruiser 55mph +.
     
  2. squirrel
    Joined: Sep 23, 2004
    Posts: 55,939

    squirrel
    Member

    It will indeed cruise 55+ mph.

    I've never run those gears with a stock engine, but that's probably a big enough engine to pull them without too much trouble. It's about like having an automatic overdrive and gears in the low-mid 3s, as far as cruising rpm. Off the line, it's like driving with a Powerglide. If the trans starts out in 2nd normally, you probably want to drop it into low then upshift.

    You gotta try it and see how you like it. You can find 2.75 and 3.00 gears pretty easily if you don't like it.
     
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  3. DrewModelA
    Joined: Oct 26, 2014
    Posts: 36

    DrewModelA
    Member

    I have a 3.10 gear now, but with a 215/75r14 tire the rpms are a little high for my liking and the cost to put an O.D. Trans behind an FE is too much.


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  4. squirrel
    Joined: Sep 23, 2004
    Posts: 55,939

    squirrel
    Member

    2.75 would drop the RPM by a couple hundred rpm at highway speed, the 2.50 will drop it more like 500 rpm.

    Like I said, you gotta try it and see how you like it.
     
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  5. Heck those old 352 curso fords had 3.00 gears and most with a long enuf road could hide the speedometer needle. I liked then with a 355 or 370 rear gear. those 250 rear gears are gonna lug the engine to death and burn the clutches out of that green dot cursomatic.
     
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  6. RichFox
    Joined: Dec 3, 2006
    Posts: 10,020

    RichFox
    Member Emeritus

    I had 2.47s in my Bonneville car. Worked good. Has 2.75s in my F100. Hated them. Didn't last long.
     
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  7. 1934coupe
    Joined: Feb 22, 2007
    Posts: 5,051

    1934coupe
    Member

    What do you concider " the rpms are a little high " lugging an engine down is as bad as it revving too high. Those tires are not that short maybe 27" - 28" nothing like a 50 or 60 series tire. What exactly are you looking for RPM wise?

    Pat
     
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  8. DrewModelA
    Joined: Oct 26, 2014
    Posts: 36

    DrewModelA
    Member

    I’m twisting close to 2500 at 60mph


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  9. Atwater Mike
    Joined: May 31, 2002
    Posts: 11,625

    Atwater Mike
    Member

    My F100 has a 3.00 ratio 9 inch, is adequate for highway. Previously had a 3.70, great in town, but was singing 'soprano' at 70+ on the freeway!
     
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  10. woodiewagon46
    Joined: Mar 14, 2013
    Posts: 2,269

    woodiewagon46
    Member
    from New York

    I have 2.75 gears in my Deuce roadster and I can cruise at 75 MPH and my motor is hardly breathing at about 2200 RPM. I think the days of building cars with 4.11 and 4.56 gears are over. Most guys I know are very content just cruising along. One of the local guys has a big block with 4.56 gears and nobody wants to travel with him. He complains that if we all drive at about 75, his motor is screaming at about 4200 RPM and he has to stop for gas every hour.
     
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  11. FityFive
    Joined: Aug 9, 2010
    Posts: 338

    FityFive
    Member

    I put 2.50 gears in my wife’s 1960 Thunderbird (FE with cruisomatic) and shortly swapped them out for 2.75 gears which I like much better.
     
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  12. Tim
    Joined: Mar 2, 2001
    Posts: 17,095

    Tim
    Member
    from KCMO

    I’d think 2500 around 60 would be pretty ideal. This isn't a new Honda that wants to cruise at 1500 rpm.

    Yeah it sounds like it’s rev’d up kinda high if you grew up with a low rpm cruising car. It’s fine man. Any higher gear and that things gonna fall on its face.
     
  13. oldiron 440
    Joined: Dec 12, 2018
    Posts: 3,299

    oldiron 440
    Member

    Just going to make the converter work harder and put more heat in the transmission.
     
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  14. DrewModelA
    Joined: Oct 26, 2014
    Posts: 36

    DrewModelA
    Member

    My bird is a ‘60 as well. I’m only about 5 miles from the interstate. Everywhere I go the speed limit is 70 I’d just like to be able to get on the freeway and not get run over by everyone doing 80+, that’s part of the reason I sold my model A roadster with 3.78’s. I also plan on hitting a lot of shows outside the state, a lot of interstate driving.


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  15. And here I was thinking that the 336 rear gears in the Dana 44 in my 66 GMC are a bit too tall. Its not bothered to run 80 MPH. don't have a tach. and Im deaf anyway so let it wind a bit . I was using a 66 chevy 3/4 ton and the pinion bearing went out. 456 gears. the only other chunk I had was under a 1950 one ton. Pulled it out and my sons where looking at it. they said dad you cant put that in your 66 its got 538 gears. I replied hide and watch me! I had a set of 19.5 tires mounted on 8 hole wheels to put on it so it worked out ok.
     
  16. Back in the 60,s the speed limits where all 60 to 75 MPH. and everyone drove the speed limit or 5 MPH above with those factory stock rear ratios. turn up the radio and let it have a bit of RPM.
     
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  17. jimmy six
    Joined: Mar 21, 2006
    Posts: 14,799

    jimmy six
    ALLIANCE MEMBER

    2.50's are going to feel dead. I have 2.74's, a cruise-o with a 26.5 tire and am very happy. Unless your working with a baby bird I probably wouldn't do it. It will also cause more heat in the converter too. My car is 3200# if 58+ yours is heavier.
     
  18. liliysdad
    Joined: Apr 1, 2013
    Posts: 98

    liliysdad
    Member
    from Oklahoma

    With 3.25s , a 3spd, and 26" tall tires behind a 390, I feel like my F100 is geared way too high. I cannot imagine 2.50s.
     
  19. Just after the national speed limit was set at 55 MPH. I was driving a 63 ford unibody truck with a 430 MEL and automatic. It had 390 rear gears. I was creeping along and seen a state trooper setting alongside the highway. no speedometer. but I was just crawling along. He stopped me and gave me a ticket 61 MPH in a 55 MPH zone.
     
  20. desotot
    Joined: Jan 29, 2008
    Posts: 2,036

    desotot
    Member

    I have two 49 mercs the finished one has a nailhead with a 400 trans and 205 75 15 tire and 3.00 gears. When I cruise at 80 mph my wife asks why is the engine running so fast? Guess a person does get used to trannys with OD. When I was a young kid I had my dads 63 merc Monterey with a 352 4 bbl and 3.00 s up to 120 mph and it was still climbing when I pulled my foot out of it.
     
  21. Pontmerc
    Joined: Jul 13, 2013
    Posts: 312

    Pontmerc
    Member
    from Finland

    I got 2.91 rear and 235/75-15 tires in my 57 turnpike cruiser.
    it cruises very easily 70mph . still accelerates fast enough on stand still.
    got original cruiso which starts second if not floored.
     
  22. squirrel
    Joined: Sep 23, 2004
    Posts: 55,939

    squirrel
    Member

    fwiw, I just swapped from the original 4.56 gears to the optional 4.11 in the Hudson. It has a pretty serious overdrive, so it was like having 3.10 gears and no overdrive, now it's like having 2.75 with no overdrive. I haven't driven it enough to get a good feel for it, but it does seem more comfy at 70-75 now. Previously I mostly drove around 65, and yeah, everyone passes you on the highway if you're going that speed
     
  23. town sedan
    Joined: Aug 18, 2011
    Posts: 1,290

    town sedan
    Member

    My '64 Galaxie with a 352 would easily cruise at 90 to 95 MPH with 3.00:1 gears and tires about the size you have.
    The 215/75R14 tire stands about 26.6 to 26.7" tall.
    With 2.50:1 gears you'll be turning a little under 1900 RPM + a little slip from the converter and it will be nearer 1950 to 2000 RPM.
    Fine for the highway, but a dog getting there. If you go with the 2.50:1 gears I'd recommend a crankshaft from a 410FE / 428FE and or a C6 transmission with a wide ratio gear set.
    As other have said you might be happier with 2.75 or 3.00:1 gears.
    -Dave
     
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  24. Jalopy Joker
    Joined: Sep 3, 2006
    Posts: 31,179

    Jalopy Joker
    Member

    2:50/stock 352 = gutless wonder from a dead stop - used to have link to a site that you entered tire diam/transmission used/gear ratio/MPH= RPM - can not find now
     
    Last edited: Aug 30, 2019
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  25. DrewModelA
    Joined: Oct 26, 2014
    Posts: 36

    DrewModelA
    Member

    Thanks for the info everyone. I’ll try them out and see how I like them. I ran a 318 duster for years with a 2.45 gear and 28in tires, and i also ran a Catalina with a 389 with 2.56 and 26in tire. I guess we’ll see how it goes, if I don’t like it I can pop the 3.10 back in.


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  26. el Scotto
    Joined: Mar 3, 2004
    Posts: 4,698

    el Scotto
    Member
    from Tracy, CA

    I had a Duster with the exact combo in high school, swapped a 360 four barrel intake, Thermoquad and a few other parts onto it and it had a top end that made my friends piss their pants! :D
     
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  27. squirrel
    Joined: Sep 23, 2004
    Posts: 55,939

    squirrel
    Member

    For years I've been meaning to put some 2.76 gears in my wife's Dart, the 3.23s are kind of severe for highway driving....with 60 series 14" tires
     
  28. DrewModelA
    Joined: Oct 26, 2014
    Posts: 36

    DrewModelA
    Member

    I eventually did a built 360 in that duster, but I had swapped to 3.55. When it had the 2.45 though the top end was just as you described


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  29. Black Panther
    Joined: Jan 6, 2010
    Posts: 2,133

    Black Panther
    Member
    from SoCal

    There were many thousands of 75 to 79 or so Trans Ams that had 400 Pontiac motors and anemic CA spec Olds 403s. What did they have in common? Many had 2.41 rear gears. A turbo 350 and those gears. Your 352 should have plenty of torque to move that T Bird no problem...its not a hot rod anyway. I just picked up a 1961 Chrysler and looking at what the tallest gearset is I can find. For the 8 3/4" Mopar looks like 2.76. I'll happily run those..lastly..years ago I had a 1968 Firebird 400 that had a 2.56 rear gear. Loved it. Plenty of torque for acceleration and you couldn't hear the engine on the freeway. Just road and tire noise. Most usable old car I've had.
     
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  30. bill gruendeman
    Joined: Jun 18, 2019
    Posts: 807

    bill gruendeman
    Member

    I have 308s with a taller tire ( 235 70 15 ) , the sweet spot is 70 to 75 mph. I would think 300s with a taller tire should be golden. Tire die. makes a bigger difference than you would think
     
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