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9''ford 2.50 ratio , you run one??

Discussion in 'The Hokey Ass Message Board' started by ryno, Mar 22, 2013.

  1. ryno
    Joined: Oct 6, 2005
    Posts: 3,470

    ryno
    Member

    like the title says, any of you guys run 2.50 ratio ring and pinion in a 9" before. i have a 3rd member out of ? i got it for the unibody f-100. i'm currently running a 3.25 and it really sucks on the highway. i'm getting about 12 mpg. with the round up coming up i'm thinking about trying out the 2.50's

    i guess my question comes in, have you been happy with the performance out of the 2.50's?

    i looked it all up on randy's ring and pinion site on his calculator. with my current tire 25" tall, cruise o matic 3 speed auto i'm turning about 3140 rpm at 70 mph, with a 2.50 gear i'm at 2415 rpm. i'm just afraid my little 289, although built and runs ok now, will be pissed around town with that tall gear.
     
  2. Tnomoldw
    Joined: Dec 5, 2012
    Posts: 1,563

    Tnomoldw
    Member

    :):cool:Try running in town in 2nd gear .:)12 mph per gallon , what a hog! Get a vacuum gauge and follow it,
     
  3. badshifter
    Joined: Apr 28, 2006
    Posts: 3,468

    badshifter
    Member

    I did that gear on my 55 ford with a Chevy 305 years ago. Pretty embarrassing to drive a hot rod that won't spin a tire on wet pavement and it required just about full throttle to run freeway speeds. You need torque for a tall gear like that to work. Oh, mileage sucked because of having to bury the throttle all the time to get and keep moving.l
     
  4. Hnstray
    Joined: Aug 23, 2009
    Posts: 12,334

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL

    Have you considered taller tires?


    Ray
     

  5. ryno
    Joined: Oct 6, 2005
    Posts: 3,470

    ryno
    Member

    what size tire where you running though?
    i think thats what will help me, my tires are really short only25" tall.
     
  6. Perfect candidate for OD
    Taller tires an option for you ?
     
  7. ryno
    Joined: Oct 6, 2005
    Posts: 3,470

    ryno
    Member

    nope. chassis is set up to run that size. id really like to run a 5 speed, but i'm too busy to do that. have had this set sitting now for a while and am just curious as to what it will pro form like.
     
  8. blyndgesser
    Joined: Jan 2, 2011
    Posts: 167

    blyndgesser
    Member
    from Georgia

    Depends on whether your 289 is built to take advantage of low rpm. Most aren't.
     
  9. badshifter
    Joined: Apr 28, 2006
    Posts: 3,468

    badshifter
    Member

    Mine were 26.5 tall.
     
  10. George
    Joined: Jan 1, 2005
    Posts: 7,577

    George
    Member

    Had an O/T Ford S/W that was fine around town but wasn't doing good pulling a car on a trailer, turned out it had 2.25s!:eek:
     
  11. Hnstray
    Joined: Aug 23, 2009
    Posts: 12,334

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL

    Not knowing all the many variables about your truck, it is hard to say what may serve you best in gaining fuel economy........however, one thing is pretty well fixed....the wind resistance (aka drag coefficent)........that truck is pretty blunt in front and wind resistance increases as the square of the speed.....meaning, if you double the speed, the wind resistance is four times greater.

    The upshot of all that is, I seriously doubt a 289 will 'pull' a 2.50 axle at speed and show any improvement in mpg. There are 2.79 and 3.00 ratios that are very common in Fords.

    Ray
     
  12. trollst
    Joined: Jan 27, 2012
    Posts: 2,092

    trollst
    ALLIANCE MEMBER

    I'm with Ray, I got a 2:20 in my 36 ford pickup, 327 engine, 350 turbo trans, truck weighs 2770 pounds, 225-75 tire on the rear, at 60 mph I get decent mileage, push it harder, get poorer mileage. Stick with what you got, slow down, take your time.
     
  13. hoop98
    Joined: Jan 23, 2013
    Posts: 1,362

    hoop98
    Member
    from Texas

    You are probably in the power circuit on the carb, power valve isssue or something, figure that out before you change gears.
     
  14. GassersGarage
    Joined: Jul 1, 2007
    Posts: 4,727

    GassersGarage
    Member

    I went from a 3:50 to a 2:74, not for mileage, but because everyone runs at 80 around here.
     
  15. Drive Em
    Joined: Aug 25, 2006
    Posts: 1,748

    Drive Em
    Member

    Yes, I ran them in my '70 Mach 1 for years. I had a four speed in it, and I would run the car in third gear around town, and shift into fourth on the highway. It is very do-able. Alot of cars in the 80's had very tall gears with small V-8's or even V-6's.
     
  16. hoop98
    Joined: Jan 23, 2013
    Posts: 1,362

    hoop98
    Member
    from Texas

    The secret to mileage with a tall gear is delaying power enrichment and maximizing vacuum advance. This minimizes friction and pumping losses. As soon as that power valve/power piston moves fuel burn goes up ~ 20 pct. If you have a mechanical power circuit you must figure out how to delay it.

    Then lean the primaries to misfire point and back a couple.

    A thermal Air Cleaner lets you jet for 100 degree air, otherwise if you jet for 60 you will be too rich at 100. When you go past 2/3 throttle you can go rich and cold air, that will not hurt steady hiway mileage.

    PS Run 195-210 water temp. 240 - 260 oil.
     
    Last edited: Mar 22, 2013
  17. Cruiser
    Joined: May 29, 2006
    Posts: 2,240

    Cruiser
    Member

    I ran a 283 SBC, 350 tranny, Edlebrook carb with 3:25 Ford 9" and my mileage was 24mpg highway. The 3:25 is a great cruising gear and gets great mileage. If, your getting only 12mpg your troubles are else where in your set up.

    CRUISER :cool:
     
  18. ryno
    Joined: Oct 6, 2005
    Posts: 3,470

    ryno
    Member

    And drivability was still cool?

    I understand all the other comments,and thank you all.
    But remember the tire size is a huge difference here. I think my mpg is so low because I'm spinning the 289 to 3k plus at 70 mph. Running the hwy out here the speed limit is 75. Rigs run 80+. Even if my mileage stayed the same,but it was more drivable I'd be happy. I'm hitting 3 rd gear around town about 35 mph.
     
  19. Throw it on that billybadass trailer of yours and haul it to Austin(I won't tell:eek:)--OD it when ya get back and have time ;)
     
  20. hoop98
    Joined: Jan 23, 2013
    Posts: 1,362

    hoop98
    Member
    from Texas

    You are burning about 100 HP worth of fuel per hour. That's way more than needed...I think you have a major fueling issue
     
  21. ryno
    Joined: Oct 6, 2005
    Posts: 3,470

    ryno
    Member

    no thanks.
    shit the super duty only gets 7 mpg!
     
  22. I was getting 15.2 mpg with350ci 2x4, 4.11, th350, 2000 lbs but still that was combined city/hi-way. It should be doing better than 12 mpg with those gears, by the way I did switch to 3.25's for easier hi-way rpms but never rechecked the mpg.
     
  23. Fiddytree
    Joined: Sep 7, 2008
    Posts: 204

    Fiddytree
    Member
    from Durango

    70 torino - 460/toploader and a 2.5 - not real peppy off the line.

    53 F100 500hp 460/ TKO 600RR and 2.5 - it will get 20mpg . . . but who wants to drive like that?

    As stated, you'll want some torque to run that tall a gear.
     
  24. mattrod68
    Joined: Jan 22, 2007
    Posts: 524

    mattrod68
    Member

    you have to remember that most of these guys getting better mileage than you are driving somewhat(at least more than yours) aerodynamic cars. any thing is better than that brick of an f100 (ask me how i know)

    im all for changing gears to make the rpms go down at freeway speeds. i went to a 3:25 from a 3:79 in my 66 f100 and it made freeway cruising much more comfortable. i turn about 2700 at 70, but i run a very tall rear tire compared to yours 235/75 15

    But it didnt help my mileage very noticably, i get 10 if im in it, i get 10 if i baby it. you cant fight aerodynamics no matter how hard you try. you already get better mileage than your tow rig.

    im thinking of switching to a 3:00 i have just to get the rpm's down some more but i wouldn't go any lower and i have a mildly hopped up big block.

    it either gonna suck around town or suck on the freeway with out an overdrive, thats why they invented them. even with an overdrive i wouldnt expect you to increase your milage by more that 2 or 3, and that is only about a 250-300 dollar savings every 5,000 miles or so. how much are you realistically gonna drive the truck?

    just my rambling two cents

    matt
     
  25. daddio211
    Joined: Aug 26, 2008
    Posts: 6,014

    daddio211
    Member

    Two setups that are typically "efficieny" and you get that kinda mileage? Methinks fuel delivery isn't the problem, methinks it may be related to your right foot!

    Sent from my DROID device using the TJJ mobile app
     
  26. RichFox
    Joined: Dec 3, 2006
    Posts: 10,020

    RichFox
    Member Emeritus

    My 77 F100 with a 351M and C6 came with a 2.47 gear and it really sucked. Gas and everything else. Now in my Bonneville car they were good.
     
  27. gimpyshotrods
    Joined: May 20, 2009
    Posts: 21,907

    gimpyshotrods
    ALLIANCE MEMBER

    Gears as tall as 2.50:1, and similar were largely a band-aid attempt to improve mileage during the oil crisis. They were quickly abandoned with the advent of the common overdrive transmissions, with the overdrive as an additional gear. You will get far more drive-ability from a modern-era overdrive transmission, with that additional gear, than you would by putting a tall gear behind a 3-speed, non-overdrive transmission.

    By adding more gears, you are expanding the range of operational efficiency of the vehicle. By simply going to a tall rear gear, you are just shifting the range efficiency to a higher MPH range, at the expense of the lower MPH range.

    This is why my Falcon is in the process of getting a 5-speed, and my Model A has a 6-speed.

    Of course, you need to match the engine output, transmission gear ratios, rear end gear ratio, tire size, considering vehicle weight, but adding more gears in the transmission always beats a tall rear end ratio.

    With more gears, you can have maximum performance AND maximum efficiency. Why give up one for the other, when you can have both?
     
  28. PackardV8
    Joined: Jun 7, 2007
    Posts: 970

    PackardV8
    Member

    I once ran a 2.80 rear gear with 15" tires in a '66 Falcon 289". Regularly got 20 MPG.

    As mentioned, if you're only getting 12 MPG, there's a problem with the carb or distributor or brakes dragging or toe in or something else.

    Fix all those, change the rear gear and the frontal area stays the same. A WAG says changing from 3.25 down to 2.50 might give you another couple MPG better, but as mentioned previously, it will require tuning the carb and ignition advance to max the improvement.

    That's why overdrive trannies exist. Changing the rear gear is like trying to make a string longer by cutting a piece off one end and tying it on the other. It just move the problem somewhere else.

    Bottom line for you - yes, a 2.50 will be a bit doggy off the line, but not really a problem. The torque converter will crutch it better than the 3-speed standard I ran for years. If you've got the rear, it is not an irreversible decision. Put in the 2.50 and if you really don't like it, put back the 3.25.

    jack vines

    jack vines
     
  29. ryno
    Joined: Oct 6, 2005
    Posts: 3,470

    ryno
    Member

    Super duty is v10 with 513 gears and 38" tires. 7 towing 10k or pussy foot around town.

    I pussed out on the 250 gear swap today. I'm gonna look for a set of 300 and try those. Or just wait for time and do a 5 speed.

    Thanks for all the comments.
     
  30. EZ Cool
    Joined: Nov 17, 2011
    Posts: 265

    EZ Cool
    Alliance Vendor
    from Slaton TX

    When I was putting my '50 sedan delivery together I put in a second gen Camaro rear in it gear ratio unknown. 401 nailhead pulled it pretty good so I wasnt to concerned about the ratio.

    I later ran across a 3.08 posi at a swap meet so I put it in. I pulled all the brakes and axles to change the rear cause I already had new brakes in the one in the car. When I pulled the cover to remove the c clips I found out it was a 2.56 ratio.

    After putting in the 3.08 posi I wasnt so happy about its crusing RPM although off the line performance was much better. Nailhead's pull hard starting right off of idle but run out of air fast at higher rpms

    I ran across a Gear Vendors OD at another swap meet and put it in. Final drive is now 2.47. I got the best of both worlds now. It all depends on where your engine makes it power then gear accordingly.
     

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